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	$40.53	13.425%	$45.9712	$45.97	$45.95	$46.00
Purchase #2	$149.54	7.356%	$160.5402	$160.54	$160.55	$160.50
Purchase #3	$53.28	12.851%	$60.127	$60.13	$60.15	$60.10
Purchase #4	$180.53	11.285%	$200.9028	$200.90	$200.90	$200.90
Purchase #5	$228.35	9.172%	$249.2943	$249.29	$249.30	$249.30
Purchase #6	$120.76	9.251%	$131.9315	$131.93	$131.95	$131.90
Purchase #7	$77.65	11.543%	$86.6131	$86.61	$86.60	$86.60
7 purchase totals =	$850.64		$935.3801	$935.37	$935.40	$935.30