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	$228.73	9.518%	$250.5005	$250.50	$250.50	$250.50
Purchase #2	$96.33	10.283%	$106.2356	$106.24	$106.25	$106.20
Purchase #3	$182.56	5.873%	$193.2817	$193.28	$193.30	$193.30
Purchase #4	$171.54	6.316%	$182.3745	$182.37	$182.35	$182.40
Purchase #5	$24.69	10.796%	$27.3555	$27.36	$27.35	$27.40
Purchase #6	$147.56	3.144%	$152.1993	$152.20	$152.20	$152.20
Purchase #7	$95.35	5.165%	$100.2748	$100.27	$100.25	$100.30
7 purchase totals =	$946.76		$1,012.2219	$1,012.22	$1,012.20	$1,012.30