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	$73.70	13.217%	$83.4409	$83.44	$83.45	$83.40
Purchase #2	$153.42	11.608%	$171.229	$171.23	$171.25	$171.20
Purchase #3	$167.52	8.677%	$182.0557	$182.06	$182.05	$182.10
Purchase #4	$41.95	3.809%	$43.5479	$43.55	$43.55	$43.50
Purchase #5	$71.80	13.811%	$81.7163	$81.72	$81.70	$81.70
Purchase #6	$100.56	5.401%	$105.9912	$105.99	$106.00	$106.00
Purchase #7	$173.63	6.450%	$184.8291	$184.83	$184.85	$184.80
7 purchase totals =	$782.58		$852.8101	$852.82	$852.85	$852.70