Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$225.50	12.443%	$253.559	$253.56	$253.55	$253.60
Purchase #2	$178.66	3.691%	$185.2543	$185.25	$185.25	$185.30
Purchase #3	$246.50	9.314%	$269.459	$269.46	$269.45	$269.50
Purchase #4	$248.82	11.827%	$278.2479	$278.25	$278.25	$278.20
Purchase #5	$131.86	11.790%	$147.4063	$147.41	$147.40	$147.40
Purchase #6	$227.52	9.147%	$248.3313	$248.33	$248.35	$248.30
Purchase #7	$139.76	7.801%	$150.6627	$150.66	$150.65	$150.70
7 purchase totals =	$1,398.62		$1,532.9205	$1,532.92	$1,532.90	$1,533.00