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	$227.56	7.160%	$243.8533	$243.85	$243.85	$243.90
Purchase #2	$118.51	7.214%	$127.0593	$127.06	$127.05	$127.10
Purchase #3	$60.49	7.505%	$65.0298	$65.03	$65.05	$65.00
Purchase #4	$97.28	8.145%	$105.2035	$105.20	$105.20	$105.20
Purchase #5	$210.26	5.499%	$221.8222	$221.82	$221.80	$221.80
Purchase #6	$87.32	3.256%	$90.1631	$90.16	$90.15	$90.20
Purchase #7	$131.30	13.562%	$149.1069	$149.11	$149.10	$149.10
7 purchase totals =	$932.72		$1,002.2381	$1,002.23	$1,002.20	$1,002.30