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	$235.52	3.243%	$243.1579	$243.16	$243.15	$243.20
Purchase #2	$39.40	10.134%	$43.3928	$43.39	$43.40	$43.40
Purchase #3	$158.78	9.253%	$173.4719	$173.47	$173.45	$173.50
Purchase #4	$197.81	10.632%	$218.8412	$218.84	$218.85	$218.80
Purchase #5	$234.73	10.417%	$259.1818	$259.18	$259.20	$259.20
Purchase #6	$109.55	3.453%	$113.3328	$113.33	$113.35	$113.30
Purchase #7	$37.35	8.663%	$40.5856	$40.59	$40.60	$40.60
7 purchase totals =	$1,013.14		$1,091.9640	$1,091.96	$1,092.00	$1,092.00