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	$111.86	12.857%	$126.2418	$126.24	$126.25	$126.20
Purchase #2	$102.40	7.398%	$109.9756	$109.98	$110.00	$110.00
Purchase #3	$243.73	11.669%	$272.1709	$272.17	$272.15	$272.20
Purchase #4	$81.70	10.601%	$90.361	$90.36	$90.35	$90.40
Purchase #5	$196.90	7.182%	$211.0414	$211.04	$211.05	$211.00
Purchase #6	$123.72	5.134%	$130.0718	$130.07	$130.05	$130.10
Purchase #7	$233.52	9.712%	$256.1995	$256.20	$256.20	$256.20
7 purchase totals =	$1,093.83		$1,196.0620	$1,196.06	$1,196.05	$1,196.10