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	$140.99	7.362%	$151.3697	$151.37	$151.35	$151.40
Purchase #2	$52.56	5.252%	$55.3205	$55.32	$55.30	$55.30
Purchase #3	$244.97	3.629%	$253.86	$253.86	$253.85	$253.90
Purchase #4	$130.33	4.503%	$136.1988	$136.20	$136.20	$136.20
Purchase #5	$123.45	10.386%	$136.2715	$136.27	$136.25	$136.30
Purchase #6	$244.61	7.829%	$263.7605	$263.76	$263.75	$263.80
Purchase #7	$101.71	12.634%	$114.56	$114.56	$114.55	$114.60
7 purchase totals =	$1,038.62		$1,111.3410	$1,111.34	$1,111.25	$1,111.50