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	$236.95	3.676%	$245.6603	$245.66	$245.65	$245.70
Purchase #2	$129.62	13.253%	$146.7985	$146.80	$146.80	$146.80
Purchase #3	$146.68	3.607%	$151.9707	$151.97	$151.95	$152.00
Purchase #4	$198.38	7.569%	$213.3954	$213.40	$213.40	$213.40
Purchase #5	$14.72	7.304%	$15.7951	$15.80	$15.80	$15.80
Purchase #6	$56.63	9.222%	$61.8524	$61.85	$61.85	$61.90
Purchase #7	$189.88	3.676%	$196.86	$196.86	$196.85	$196.90
7 purchase totals =	$972.86		$1,032.3324	$1,032.34	$1,032.30	$1,032.50