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	$77.92	9.668%	$85.4533	$85.45	$85.45	$85.50
Purchase #2	$200.49	13.234%	$227.0228	$227.02	$227.00	$227.00
Purchase #3	$234.65	12.630%	$264.2863	$264.29	$264.30	$264.30
Purchase #4	$92.91	13.254%	$105.2243	$105.22	$105.20	$105.20
Purchase #5	$58.53	7.311%	$62.8091	$62.81	$62.80	$62.80
Purchase #6	$78.74	12.694%	$88.7353	$88.74	$88.75	$88.70
Purchase #7	$213.58	10.229%	$235.4271	$235.43	$235.45	$235.40
7 purchase totals =	$956.82		$1,068.9582	$1,068.96	$1,068.95	$1,068.90