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	$191.45	9.197%	$209.0577	$209.06	$209.05	$209.10
Purchase #2	$56.49	5.617%	$59.663	$59.66	$59.65	$59.70
Purchase #3	$197.43	7.556%	$212.3478	$212.35	$212.35	$212.30
Purchase #4	$65.26	10.535%	$72.1351	$72.14	$72.15	$72.10
Purchase #5	$71.92	12.443%	$80.869	$80.87	$80.85	$80.90
Purchase #6	$88.27	11.245%	$98.196	$98.20	$98.20	$98.20
Purchase #7	$91.39	8.571%	$99.223	$99.22	$99.20	$99.20
7 purchase totals =	$762.21		$831.4916	$831.50	$831.45	$831.50