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	$170.36	8.862%	$185.4573	$185.46	$185.45	$185.50
Purchase #2	$204.88	8.519%	$222.3337	$222.33	$222.35	$222.30
Purchase #3	$79.88	7.516%	$85.8838	$85.88	$85.90	$85.90
Purchase #4	$196.72	13.732%	$223.7336	$223.73	$223.75	$223.70
Purchase #5	$247.74	8.311%	$268.3297	$268.33	$268.35	$268.30
Purchase #6	$111.37	4.285%	$116.1422	$116.14	$116.15	$116.10
Purchase #7	$164.71	7.281%	$176.7025	$176.70	$176.70	$176.70
7 purchase totals =	$1,175.66		$1,278.5828	$1,278.57	$1,278.65	$1,278.50