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	$246.90	7.106%	$264.4447	$264.44	$264.45	$264.40
Purchase #2	$47.46	5.825%	$50.2245	$50.22	$50.20	$50.20
Purchase #3	$53.51	10.644%	$59.2056	$59.21	$59.20	$59.20
Purchase #4	$191.56	7.310%	$205.563	$205.56	$205.55	$205.60
Purchase #5	$57.25	13.727%	$65.1087	$65.11	$65.10	$65.10
Purchase #6	$166.42	12.236%	$186.7832	$186.78	$186.80	$186.80
Purchase #7	$177.65	3.521%	$183.9051	$183.91	$183.90	$183.90
7 purchase totals =	$940.75		$1,015.2348	$1,015.23	$1,015.20	$1,015.20