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	$104.79	6.726%	$111.8382	$111.84	$111.85	$111.80
Purchase #2	$234.33	4.368%	$244.5655	$244.57	$244.55	$244.60
Purchase #3	$36.43	8.863%	$39.6588	$39.66	$39.65	$39.70
Purchase #4	$216.69	13.147%	$245.1782	$245.18	$245.20	$245.20
Purchase #5	$123.62	5.861%	$130.8654	$130.87	$130.85	$130.90
Purchase #6	$43.89	5.483%	$46.2965	$46.30	$46.30	$46.30
Purchase #7	$209.33	9.790%	$229.8234	$229.82	$229.80	$229.80
7 purchase totals =	$969.08		$1,048.2260	$1,048.24	$1,048.20	$1,048.30