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	$165.85	8.153%	$179.3718	$179.37	$179.35	$179.40
Purchase #2	$198.74	5.532%	$209.7343	$209.73	$209.75	$209.70
Purchase #3	$107.89	9.585%	$118.2313	$118.23	$118.25	$118.20
Purchase #4	$175.27	5.259%	$184.4874	$184.49	$184.50	$184.50
Purchase #5	$220.71	5.819%	$233.5531	$233.55	$233.55	$233.60
Purchase #6	$73.59	5.532%	$77.661	$77.66	$77.65	$77.70
Purchase #7	$185.41	12.416%	$208.4305	$208.43	$208.45	$208.40
7 purchase totals =	$1,127.46		$1,211.4694	$1,211.46	$1,211.50	$1,211.50