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	$67.74	6.630%	$72.2312	$72.23	$72.25	$72.20
Purchase #2	$169.88	12.549%	$191.1982	$191.20	$191.20	$191.20
Purchase #3	$159.36	8.825%	$173.4235	$173.42	$173.40	$173.40
Purchase #4	$28.31	7.743%	$30.502	$30.50	$30.50	$30.50
Purchase #5	$248.69	11.218%	$276.588	$276.59	$276.60	$276.60
Purchase #6	$215.75	5.613%	$227.86	$227.86	$227.85	$227.90
Purchase #7	$122.66	9.360%	$134.141	$134.14	$134.15	$134.10
7 purchase totals =	$1,012.39		$1,105.9439	$1,105.94	$1,105.95	$1,105.90