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	$242.68	5.158%	$255.1974	$255.20	$255.20	$255.20
Purchase #2	$58.76	9.803%	$64.5202	$64.52	$64.50	$64.50
Purchase #3	$152.45	13.398%	$172.8753	$172.88	$172.90	$172.90
Purchase #4	$68.63	13.841%	$78.1291	$78.13	$78.15	$78.10
Purchase #5	$60.76	3.456%	$62.8599	$62.86	$62.85	$62.90
Purchase #6	$159.52	3.619%	$165.293	$165.29	$165.30	$165.30
Purchase #7	$194.89	4.812%	$204.2681	$204.27	$204.25	$204.30
7 purchase totals =	$937.69		$1,003.1430	$1,003.15	$1,003.15	$1,003.20