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	$226.59	10.440%	$250.246	$250.25	$250.25	$250.20
Purchase #2	$103.90	4.614%	$108.6939	$108.69	$108.70	$108.70
Purchase #3	$128.86	3.427%	$133.276	$133.28	$133.30	$133.30
Purchase #4	$99.55	12.129%	$111.6244	$111.62	$111.60	$111.60
Purchase #5	$218.46	11.362%	$243.2814	$243.28	$243.30	$243.30
Purchase #6	$202.50	4.258%	$211.1225	$211.12	$211.10	$211.10
Purchase #7	$81.80	10.406%	$90.3121	$90.31	$90.30	$90.30
7 purchase totals =	$1,061.66		$1,148.5563	$1,148.55	$1,148.55	$1,148.50