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	$104.91	4.811%	$109.9572	$109.96	$109.95	$110.00
Purchase #2	$88.72	7.148%	$95.0617	$95.06	$95.05	$95.10
Purchase #3	$20.78	4.468%	$21.7085	$21.71	$21.70	$21.70
Purchase #4	$35.61	11.498%	$39.7044	$39.70	$39.70	$39.70
Purchase #5	$6.68	8.225%	$7.2294	$7.23	$7.25	$7.20
Purchase #6	$127.73	13.257%	$144.6632	$144.66	$144.65	$144.70
Purchase #7	$92.53	12.515%	$104.1101	$104.11	$104.10	$104.10
7 purchase totals =	$476.96		$522.4345	$522.43	$522.40	$522.50