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	$102.84	8.632%	$111.7171	$111.72	$111.70	$111.70
Purchase #2	$154.40	11.815%	$172.6424	$172.64	$172.65	$172.60
Purchase #3	$98.25	5.154%	$103.3138	$103.31	$103.30	$103.30
Purchase #4	$123.76	4.728%	$129.6114	$129.61	$129.60	$129.60
Purchase #5	$110.41	13.522%	$125.3396	$125.34	$125.35	$125.30
Purchase #6	$219.27	13.357%	$248.5579	$248.56	$248.55	$248.60
Purchase #7	$140.41	4.242%	$146.3662	$146.37	$146.35	$146.40
7 purchase totals =	$949.34		$1,037.5484	$1,037.55	$1,037.50	$1,037.50