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	$7.46	4.118%	$7.7672	$7.77	$7.75	$7.80
Purchase #2	$80.78	6.151%	$85.7488	$85.75	$85.75	$85.70
Purchase #3	$142.48	4.400%	$148.7491	$148.75	$148.75	$148.70
Purchase #4	$139.42	12.485%	$156.8266	$156.83	$156.85	$156.80
Purchase #5	$146.40	13.251%	$165.7995	$165.80	$165.80	$165.80
Purchase #6	$151.88	12.478%	$170.8316	$170.83	$170.85	$170.80
Purchase #7	$61.31	7.257%	$65.7593	$65.76	$65.75	$65.80
7 purchase totals =	$729.73		$801.4821	$801.49	$801.50	$801.40