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	$45.98	13.348%	$52.1174	$52.12	$52.10	$52.10
Purchase #2	$76.70	13.786%	$87.2739	$87.27	$87.25	$87.30
Purchase #3	$163.86	12.598%	$184.5031	$184.50	$184.50	$184.50
Purchase #4	$41.55	9.151%	$45.3522	$45.35	$45.35	$45.40
Purchase #5	$71.32	11.167%	$79.2843	$79.28	$79.30	$79.30
Purchase #6	$55.63	7.331%	$59.7082	$59.71	$59.70	$59.70
Purchase #7	$220.48	13.647%	$250.5689	$250.57	$250.55	$250.60
7 purchase totals =	$675.52		$758.8080	$758.80	$758.75	$758.90