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	$27.49	7.690%	$29.604	$29.60	$29.60	$29.60
Purchase #2	$82.78	8.617%	$89.9132	$89.91	$89.90	$89.90
Purchase #3	$201.42	8.685%	$218.9133	$218.91	$218.90	$218.90
Purchase #4	$52.59	7.808%	$56.6962	$56.70	$56.70	$56.70
Purchase #5	$202.65	9.600%	$222.1044	$222.10	$222.10	$222.10
Purchase #6	$235.48	12.432%	$264.7549	$264.75	$264.75	$264.80
Purchase #7	$225.93	8.408%	$244.9262	$244.93	$244.95	$244.90
7 purchase totals =	$1,028.34		$1,126.9122	$1,126.90	$1,126.90	$1,126.90