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	$92.64	11.200%	$103.0157	$103.02	$103.00	$103.00
Purchase #2	$5.80	11.337%	$6.4575	$6.46	$6.45	$6.50
Purchase #3	$100.50	12.155%	$112.7158	$112.72	$112.70	$112.70
Purchase #4	$102.66	6.533%	$109.3668	$109.37	$109.35	$109.40
Purchase #5	$237.75	7.209%	$254.8894	$254.89	$254.90	$254.90
Purchase #6	$52.61	5.813%	$55.6682	$55.67	$55.65	$55.70
Purchase #7	$234.71	3.178%	$242.1691	$242.17	$242.15	$242.20
7 purchase totals =	$826.67		$884.2825	$884.30	$884.20	$884.40