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	$89.52	7.860%	$96.5563	$96.56	$96.55	$96.60
Purchase #2	$235.39	9.735%	$258.3052	$258.31	$258.30	$258.30
Purchase #3	$189.89	11.672%	$212.054	$212.05	$212.05	$212.10
Purchase #4	$49.47	7.200%	$53.0318	$53.03	$53.05	$53.00
Purchase #5	$108.72	7.561%	$116.9403	$116.94	$116.95	$116.90
Purchase #6	$158.34	6.831%	$169.1562	$169.16	$169.15	$169.20
Purchase #7	$156.89	3.780%	$162.8204	$162.82	$162.80	$162.80
7 purchase totals =	$988.22		$1,068.8642	$1,068.87	$1,068.85	$1,068.90