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	$194.86	7.512%	$209.4979	$209.50	$209.50	$209.50
Purchase #2	$139.94	4.110%	$145.6915	$145.69	$145.70	$145.70
Purchase #3	$219.82	12.571%	$247.4536	$247.45	$247.45	$247.50
Purchase #4	$86.67	11.285%	$96.4507	$96.45	$96.45	$96.50
Purchase #5	$63.45	4.501%	$66.3059	$66.31	$66.30	$66.30
Purchase #6	$188.50	3.645%	$195.3708	$195.37	$195.35	$195.40
Purchase #7	$57.27	4.277%	$59.7194	$59.72	$59.70	$59.70
7 purchase totals =	$950.51		$1,020.4898	$1,020.49	$1,020.45	$1,020.60