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	$136.39	3.845%	$141.6342	$141.63	$141.65	$141.60
Purchase #2	$128.55	11.129%	$142.8563	$142.86	$142.85	$142.90
Purchase #3	$43.70	6.178%	$46.3998	$46.40	$46.40	$46.40
Purchase #4	$125.64	9.569%	$137.6625	$137.66	$137.65	$137.70
Purchase #5	$221.67	7.362%	$237.9893	$237.99	$238.00	$238.00
Purchase #6	$181.31	4.302%	$189.11	$189.11	$189.10	$189.10
Purchase #7	$229.33	11.764%	$256.3084	$256.31	$256.30	$256.30
7 purchase totals =	$1,066.59		$1,151.9605	$1,151.96	$1,151.95	$1,152.00