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	$34.70	7.410%	$37.2713	$37.27	$37.25	$37.30
Purchase #2	$172.30	9.431%	$188.5496	$188.55	$188.55	$188.50
Purchase #3	$127.92	11.251%	$142.3123	$142.31	$142.30	$142.30
Purchase #4	$153.28	9.287%	$167.5151	$167.52	$167.50	$167.50
Purchase #5	$166.58	11.550%	$185.82	$185.82	$185.80	$185.80
Purchase #6	$165.44	9.719%	$181.5191	$181.52	$181.50	$181.50
Purchase #7	$117.88	8.555%	$127.9646	$127.96	$127.95	$128.00
7 purchase totals =	$938.10		$1,030.9520	$1,030.95	$1,030.85	$1,030.90