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	$148.57	11.627%	$165.8442	$165.84	$165.85	$165.80
Purchase #2	$91.52	13.714%	$104.0711	$104.07	$104.05	$104.10
Purchase #3	$183.84	12.506%	$206.831	$206.83	$206.85	$206.80
Purchase #4	$80.65	7.843%	$86.9754	$86.98	$87.00	$87.00
Purchase #5	$41.94	11.314%	$46.6851	$46.69	$46.70	$46.70
Purchase #6	$54.41	8.711%	$59.1497	$59.15	$59.15	$59.10
Purchase #7	$37.67	7.404%	$40.4591	$40.46	$40.45	$40.50
7 purchase totals =	$638.60		$710.0156	$710.02	$710.05	$710.00