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	$69.64	10.696%	$77.0887	$77.09	$77.10	$77.10
Purchase #2	$169.48	9.590%	$185.7331	$185.73	$185.75	$185.70
Purchase #3	$85.68	4.312%	$89.3745	$89.37	$89.35	$89.40
Purchase #4	$61.59	4.341%	$64.2636	$64.26	$64.25	$64.30
Purchase #5	$161.26	9.485%	$176.5555	$176.56	$176.55	$176.60
Purchase #6	$209.95	6.145%	$222.8514	$222.85	$222.85	$222.90
Purchase #7	$44.42	7.765%	$47.8692	$47.87	$47.85	$47.90
7 purchase totals =	$802.02		$863.7360	$863.73	$863.70	$863.90