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	$194.45	11.132%	$216.0962	$216.10	$216.10	$216.10
Purchase #2	$35.85	13.748%	$40.7787	$40.78	$40.80	$40.80
Purchase #3	$43.38	5.679%	$45.8436	$45.84	$45.85	$45.80
Purchase #4	$175.91	6.165%	$186.7549	$186.75	$186.75	$186.80
Purchase #5	$41.48	4.297%	$43.2624	$43.26	$43.25	$43.30
Purchase #6	$54.47	11.483%	$60.7248	$60.72	$60.70	$60.70
Purchase #7	$79.98	4.366%	$83.4719	$83.47	$83.45	$83.50
7 purchase totals =	$625.52		$676.9325	$676.92	$676.90	$677.00