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	$203.49	9.223%	$222.2579	$222.26	$222.25	$222.30
Purchase #2	$135.61	9.751%	$148.8333	$148.83	$148.85	$148.80
Purchase #3	$88.76	5.867%	$93.9675	$93.97	$93.95	$94.00
Purchase #4	$105.48	6.547%	$112.3858	$112.39	$112.40	$112.40
Purchase #5	$168.35	4.179%	$175.3853	$175.39	$175.40	$175.40
Purchase #6	$179.96	10.721%	$199.2535	$199.25	$199.25	$199.30
Purchase #7	$98.79	13.227%	$111.857	$111.86	$111.85	$111.90
7 purchase totals =	$980.44		$1,063.9403	$1,063.95	$1,063.95	$1,064.10