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	$43.59	8.637%	$47.3549	$47.35	$47.35	$47.40
Purchase #2	$53.95	12.570%	$60.7315	$60.73	$60.75	$60.70
Purchase #3	$80.76	11.495%	$90.0434	$90.04	$90.05	$90.00
Purchase #4	$212.39	13.552%	$241.1731	$241.17	$241.15	$241.20
Purchase #5	$73.46	6.570%	$78.2863	$78.29	$78.30	$78.30
Purchase #6	$147.30	7.810%	$158.8041	$158.80	$158.80	$158.80
Purchase #7	$78.40	10.308%	$86.4815	$86.48	$86.50	$86.50
7 purchase totals =	$689.85		$762.8748	$762.86	$762.90	$762.90