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	$71.31	6.353%	$75.8403	$75.84	$75.85	$75.80
Purchase #2	$225.74	8.201%	$244.2529	$244.25	$244.25	$244.30
Purchase #3	$11.84	12.484%	$13.3181	$13.32	$13.30	$13.30
Purchase #4	$83.59	7.216%	$89.6219	$89.62	$89.60	$89.60
Purchase #5	$94.90	4.690%	$99.3508	$99.35	$99.35	$99.40
Purchase #6	$223.85	13.673%	$254.457	$254.46	$254.45	$254.50
Purchase #7	$13.97	7.768%	$15.0552	$15.06	$15.05	$15.10
7 purchase totals =	$725.20		$791.8962	$791.90	$791.85	$792.00