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	$122.70	7.385%	$131.7614	$131.76	$131.75	$131.80
Purchase #2	$30.33	11.310%	$33.7603	$33.76	$33.75	$33.80
Purchase #3	$236.67	10.710%	$262.0174	$262.02	$262.00	$262.00
Purchase #4	$155.54	8.384%	$168.5805	$168.58	$168.60	$168.60
Purchase #5	$135.77	12.118%	$152.2226	$152.22	$152.20	$152.20
Purchase #6	$101.75	9.808%	$111.7296	$111.73	$111.75	$111.70
Purchase #7	$105.96	12.556%	$119.2643	$119.26	$119.25	$119.30
7 purchase totals =	$888.72		$979.3361	$979.33	$979.30	$979.40