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	$36.46	4.105%	$37.9567	$37.96	$37.95	$38.00
Purchase #2	$74.65	5.760%	$78.9498	$78.95	$78.95	$78.90
Purchase #3	$115.86	5.834%	$122.6193	$122.62	$122.60	$122.60
Purchase #4	$85.41	4.412%	$89.1783	$89.18	$89.20	$89.20
Purchase #5	$236.38	11.824%	$264.3296	$264.33	$264.35	$264.30
Purchase #6	$209.74	13.780%	$238.6422	$238.64	$238.65	$238.60
Purchase #7	$191.27	7.375%	$205.3762	$205.38	$205.40	$205.40
7 purchase totals =	$949.77		$1,037.0521	$1,037.06	$1,037.10	$1,037.00