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	$215.73	12.244%	$242.144	$242.14	$242.15	$242.10
Purchase #2	$224.89	7.369%	$241.4621	$241.46	$241.45	$241.50
Purchase #3	$218.93	7.568%	$235.4986	$235.50	$235.50	$235.50
Purchase #4	$181.27	8.427%	$196.5456	$196.55	$196.55	$196.50
Purchase #5	$208.65	11.221%	$232.0626	$232.06	$232.05	$232.10
Purchase #6	$43.51	4.198%	$45.3365	$45.34	$45.35	$45.30
Purchase #7	$5.91	5.437%	$6.2313	$6.23	$6.25	$6.20
7 purchase totals =	$1,098.89		$1,199.2807	$1,199.28	$1,199.30	$1,199.20