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	$196.45	10.621%	$217.315	$217.32	$217.30	$217.30
Purchase #2	$204.30	9.387%	$223.4776	$223.48	$223.50	$223.50
Purchase #3	$53.82	9.449%	$58.9055	$58.91	$58.90	$58.90
Purchase #4	$245.93	3.338%	$254.1391	$254.14	$254.15	$254.10
Purchase #5	$175.74	8.148%	$190.0593	$190.06	$190.05	$190.10
Purchase #6	$204.57	5.364%	$215.5431	$215.54	$215.55	$215.50
Purchase #7	$73.90	11.287%	$82.2411	$82.24	$82.25	$82.20
7 purchase totals =	$1,154.71		$1,241.6807	$1,241.69	$1,241.70	$1,241.60