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	$134.39	10.813%	$148.9216	$148.92	$148.90	$148.90
Purchase #2	$104.72	10.426%	$115.6381	$115.64	$115.65	$115.60
Purchase #3	$118.67	6.652%	$126.5639	$126.56	$126.55	$126.60
Purchase #4	$167.72	11.867%	$187.6233	$187.62	$187.60	$187.60
Purchase #5	$90.91	9.391%	$99.4474	$99.45	$99.45	$99.40
Purchase #6	$221.34	3.494%	$229.0736	$229.07	$229.05	$229.10
Purchase #7	$33.99	10.741%	$37.6409	$37.64	$37.65	$37.60
7 purchase totals =	$871.74		$944.9088	$944.90	$944.85	$944.80