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	$5.53	13.524%	$6.2779	$6.28	$6.30	$6.30
Purchase #2	$93.88	9.730%	$103.0145	$103.01	$103.00	$103.00
Purchase #3	$196.51	4.624%	$205.5966	$205.60	$205.60	$205.60
Purchase #4	$33.80	9.468%	$37.0002	$37.00	$37.00	$37.00
Purchase #5	$212.45	4.752%	$222.5456	$222.55	$222.55	$222.50
Purchase #6	$247.33	12.139%	$277.3534	$277.35	$277.35	$277.40
Purchase #7	$135.51	12.632%	$152.6276	$152.63	$152.65	$152.60
7 purchase totals =	$925.01		$1,004.4158	$1,004.42	$1,004.45	$1,004.40