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	$126.66	4.814%	$132.7574	$132.76	$132.75	$132.80
Purchase #2	$234.46	13.263%	$265.5564	$265.56	$265.55	$265.60
Purchase #3	$84.58	6.200%	$89.824	$89.82	$89.80	$89.80
Purchase #4	$27.97	4.550%	$29.2426	$29.24	$29.25	$29.20
Purchase #5	$165.55	12.812%	$186.7603	$186.76	$186.75	$186.80
Purchase #6	$246.59	13.103%	$278.9007	$278.90	$278.90	$278.90
Purchase #7	$78.79	8.380%	$85.3926	$85.39	$85.40	$85.40
7 purchase totals =	$964.60		$1,068.4340	$1,068.43	$1,068.40	$1,068.50