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	$191.99	6.819%	$205.0818	$205.08	$205.10	$205.10
Purchase #2	$114.65	13.372%	$129.981	$129.98	$130.00	$130.00
Purchase #3	$168.47	11.761%	$188.2838	$188.28	$188.30	$188.30
Purchase #4	$69.54	12.391%	$78.1567	$78.16	$78.15	$78.20
Purchase #5	$221.25	7.774%	$238.45	$238.45	$238.45	$238.50
Purchase #6	$55.55	4.289%	$57.9325	$57.93	$57.95	$57.90
Purchase #7	$50.45	12.171%	$56.5903	$56.59	$56.60	$56.60
7 purchase totals =	$871.90		$954.4761	$954.47	$954.55	$954.60