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	$49.58	7.405%	$53.2514	$53.25	$53.25	$53.30
Purchase #2	$73.63	6.443%	$78.374	$78.37	$78.35	$78.40
Purchase #3	$243.91	12.732%	$274.9646	$274.96	$274.95	$275.00
Purchase #4	$141.80	4.632%	$148.3682	$148.37	$148.35	$148.40
Purchase #5	$144.59	3.608%	$149.8068	$149.81	$149.80	$149.80
Purchase #6	$105.62	10.370%	$116.5728	$116.57	$116.55	$116.60
Purchase #7	$57.71	11.127%	$64.1314	$64.13	$64.15	$64.10
7 purchase totals =	$816.84		$885.4692	$885.46	$885.40	$885.60