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	$33.70	5.700%	$35.6209	$35.62	$35.60	$35.60
Purchase #2	$55.55	11.862%	$62.1393	$62.14	$62.15	$62.10
Purchase #3	$72.61	3.689%	$75.2886	$75.29	$75.30	$75.30
Purchase #4	$83.85	9.556%	$91.8627	$91.86	$91.85	$91.90
Purchase #5	$71.64	9.850%	$78.6965	$78.70	$78.70	$78.70
Purchase #6	$71.39	5.512%	$75.325	$75.33	$75.35	$75.30
Purchase #7	$147.85	5.465%	$155.93	$155.93	$155.95	$155.90
7 purchase totals =	$536.59		$574.8630	$574.87	$574.90	$574.80