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	$205.68	7.561%	$221.2315	$221.23	$221.25	$221.20
Purchase #2	$137.47	7.736%	$148.1047	$148.10	$148.10	$148.10
Purchase #3	$31.81	3.636%	$32.9666	$32.97	$32.95	$33.00
Purchase #4	$96.79	11.682%	$108.097	$108.10	$108.10	$108.10
Purchase #5	$118.40	7.396%	$127.1569	$127.16	$127.15	$127.20
Purchase #6	$137.65	9.178%	$150.2835	$150.28	$150.30	$150.30
Purchase #7	$243.65	8.191%	$263.6074	$263.61	$263.60	$263.60
7 purchase totals =	$971.45		$1,051.4476	$1,051.45	$1,051.45	$1,051.50