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	$218.38	13.524%	$247.9137	$247.91	$247.90	$247.90
Purchase #2	$147.69	5.273%	$155.4777	$155.48	$155.50	$155.50
Purchase #3	$19.76	5.649%	$20.8762	$20.88	$20.90	$20.90
Purchase #4	$32.55	3.623%	$33.7293	$33.73	$33.75	$33.70
Purchase #5	$248.64	8.477%	$269.7172	$269.72	$269.70	$269.70
Purchase #6	$213.48	12.460%	$240.0796	$240.08	$240.10	$240.10
Purchase #7	$149.28	6.760%	$159.3713	$159.37	$159.35	$159.40
7 purchase totals =	$1,029.78		$1,127.1650	$1,127.17	$1,127.20	$1,127.20