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	$221.59	9.514%	$242.6721	$242.67	$242.65	$242.70
Purchase #2	$78.72	12.778%	$88.7788	$88.78	$88.80	$88.80
Purchase #3	$111.99	3.483%	$115.8906	$115.89	$115.90	$115.90
Purchase #4	$95.37	10.112%	$105.0138	$105.01	$105.00	$105.00
Purchase #5	$152.49	12.650%	$171.78	$171.78	$171.80	$171.80
Purchase #6	$215.42	10.336%	$237.6858	$237.69	$237.70	$237.70
Purchase #7	$147.42	5.353%	$155.3114	$155.31	$155.30	$155.30
7 purchase totals =	$1,023.00		$1,117.1325	$1,117.13	$1,117.15	$1,117.20