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	$82.80	6.628%	$88.288	$88.29	$88.30	$88.30
Purchase #2	$145.93	11.162%	$162.2187	$162.22	$162.20	$162.20
Purchase #3	$145.92	6.280%	$155.0838	$155.08	$155.10	$155.10
Purchase #4	$224.47	11.781%	$250.9148	$250.91	$250.90	$250.90
Purchase #5	$46.89	8.512%	$50.8813	$50.88	$50.90	$50.90
Purchase #6	$210.53	6.266%	$223.7218	$223.72	$223.70	$223.70
Purchase #7	$206.57	5.488%	$217.9066	$217.91	$217.90	$217.90
7 purchase totals =	$1,063.11		$1,149.0150	$1,149.01	$1,149.00	$1,149.00