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	$250.74	7.113%	$268.5751	$268.58	$268.60	$268.60
Purchase #2	$247.61	13.323%	$280.5991	$280.60	$280.60	$280.60
Purchase #3	$110.27	5.737%	$116.5962	$116.60	$116.60	$116.60
Purchase #4	$7.59	4.672%	$7.9446	$7.94	$7.95	$7.90
Purchase #5	$41.79	9.441%	$45.7354	$45.74	$45.75	$45.70
Purchase #6	$246.44	9.404%	$269.6152	$269.62	$269.60	$269.60
Purchase #7	$90.64	9.748%	$99.4756	$99.48	$99.50	$99.50
7 purchase totals =	$995.08		$1,088.5412	$1,088.56	$1,088.60	$1,088.50