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	$87.88	10.449%	$97.0626	$97.06	$97.05	$97.10
Purchase #2	$191.43	4.591%	$200.2186	$200.22	$200.20	$200.20
Purchase #3	$222.71	9.119%	$243.0189	$243.02	$243.00	$243.00
Purchase #4	$98.51	13.585%	$111.8926	$111.89	$111.90	$111.90
Purchase #5	$218.30	11.267%	$242.8959	$242.90	$242.90	$242.90
Purchase #6	$208.84	12.435%	$234.8093	$234.81	$234.80	$234.80
Purchase #7	$194.46	9.268%	$212.4826	$212.48	$212.50	$212.50
7 purchase totals =	$1,222.13		$1,342.3805	$1,342.38	$1,342.35	$1,342.40