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	$105.95	11.739%	$118.3875	$118.39	$118.40	$118.40
Purchase #2	$246.51	8.852%	$268.3311	$268.33	$268.35	$268.30
Purchase #3	$59.59	13.457%	$67.609	$67.61	$67.60	$67.60
Purchase #4	$79.50	12.604%	$89.5202	$89.52	$89.50	$89.50
Purchase #5	$107.71	4.811%	$112.8919	$112.89	$112.90	$112.90
Purchase #6	$130.33	4.588%	$136.3095	$136.31	$136.30	$136.30
Purchase #7	$154.37	9.621%	$169.2219	$169.22	$169.20	$169.20
7 purchase totals =	$883.96		$962.2711	$962.27	$962.25	$962.20