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	$96.52	4.825%	$101.1771	$101.18	$101.20	$101.20
Purchase #2	$11.73	4.861%	$12.3002	$12.30	$12.30	$12.30
Purchase #3	$19.35	7.735%	$20.8467	$20.85	$20.85	$20.80
Purchase #4	$218.89	3.397%	$226.3257	$226.33	$226.35	$226.30
Purchase #5	$155.93	5.324%	$164.2317	$164.23	$164.25	$164.20
Purchase #6	$108.98	13.127%	$123.2858	$123.29	$123.30	$123.30
Purchase #7	$93.27	7.341%	$100.117	$100.12	$100.10	$100.10
7 purchase totals =	$704.67		$748.2842	$748.30	$748.35	$748.20