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	$67.36	8.611%	$73.1604	$73.16	$73.15	$73.20
Purchase #2	$30.88	9.615%	$33.8491	$33.85	$33.85	$33.80
Purchase #3	$116.44	6.130%	$123.5778	$123.58	$123.60	$123.60
Purchase #4	$68.52	9.554%	$75.0664	$75.07	$75.05	$75.10
Purchase #5	$99.53	10.362%	$109.8433	$109.84	$109.85	$109.80
Purchase #6	$50.43	12.243%	$56.6041	$56.60	$56.60	$56.60
Purchase #7	$16.34	10.517%	$18.0585	$18.06	$18.05	$18.10
7 purchase totals =	$449.50		$490.1596	$490.16	$490.15	$490.20