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	$70.77	7.413%	$76.0162	$76.02	$76.00	$76.00
Purchase #2	$62.71	3.482%	$64.8936	$64.89	$64.90	$64.90
Purchase #3	$139.42	13.655%	$158.4578	$158.46	$158.45	$158.50
Purchase #4	$73.78	4.592%	$77.168	$77.17	$77.15	$77.20
Purchase #5	$145.31	5.320%	$153.0405	$153.04	$153.05	$153.00
Purchase #6	$13.87	11.818%	$15.5092	$15.51	$15.50	$15.50
Purchase #7	$66.90	4.718%	$70.0563	$70.06	$70.05	$70.10
7 purchase totals =	$572.76		$615.1416	$615.15	$615.10	$615.20