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	$127.99	9.628%	$140.3129	$140.31	$140.30	$140.30
Purchase #2	$173.34	13.229%	$196.2711	$196.27	$196.25	$196.30
Purchase #3	$236.31	7.315%	$253.5961	$253.60	$253.60	$253.60
Purchase #4	$236.51	7.541%	$254.3452	$254.35	$254.35	$254.30
Purchase #5	$77.80	10.837%	$86.2312	$86.23	$86.25	$86.20
Purchase #6	$86.61	12.133%	$97.1184	$97.12	$97.10	$97.10
Purchase #7	$226.28	7.446%	$243.1288	$243.13	$243.15	$243.10
7 purchase totals =	$1,164.84		$1,271.0037	$1,271.01	$1,271.00	$1,270.90