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	$171.87	11.345%	$191.3687	$191.37	$191.35	$191.40
Purchase #2	$103.86	10.302%	$114.5597	$114.56	$114.55	$114.60
Purchase #3	$97.96	12.196%	$109.9072	$109.91	$109.90	$109.90
Purchase #4	$198.71	10.748%	$220.0674	$220.07	$220.05	$220.10
Purchase #5	$174.41	10.634%	$192.9568	$192.96	$192.95	$193.00
Purchase #6	$57.82	6.301%	$61.4632	$61.46	$61.45	$61.50
Purchase #7	$151.55	3.115%	$156.2708	$156.27	$156.25	$156.30
7 purchase totals =	$956.18		$1,046.5938	$1,046.60	$1,046.50	$1,046.80