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	$176.80	5.149%	$185.9034	$185.90	$185.90	$185.90
Purchase #2	$7.42	11.199%	$8.251	$8.25	$8.25	$8.30
Purchase #3	$37.47	10.612%	$41.4463	$41.45	$41.45	$41.40
Purchase #4	$17.93	8.437%	$19.4428	$19.44	$19.45	$19.40
Purchase #5	$57.27	4.497%	$59.8454	$59.85	$59.85	$59.80
Purchase #6	$16.67	8.651%	$18.1121	$18.11	$18.10	$18.10
Purchase #7	$212.31	5.442%	$223.8639	$223.86	$223.85	$223.90
7 purchase totals =	$525.87		$556.8649	$556.86	$556.85	$556.80