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	$174.45	11.717%	$194.8903	$194.89	$194.90	$194.90
Purchase #2	$88.44	11.646%	$98.7397	$98.74	$98.75	$98.70
Purchase #3	$76.30	5.610%	$80.5804	$80.58	$80.60	$80.60
Purchase #4	$10.99	7.817%	$11.8491	$11.85	$11.85	$11.80
Purchase #5	$129.77	13.629%	$147.4564	$147.46	$147.45	$147.50
Purchase #6	$56.44	9.705%	$61.9175	$61.92	$61.90	$61.90
Purchase #7	$55.76	6.441%	$59.3515	$59.35	$59.35	$59.40
7 purchase totals =	$592.15		$654.7849	$654.79	$654.80	$654.80