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	$189.72	3.163%	$195.7208	$195.72	$195.70	$195.70
Purchase #2	$184.98	10.340%	$204.1069	$204.11	$204.10	$204.10
Purchase #3	$54.27	9.323%	$59.3296	$59.33	$59.35	$59.30
Purchase #4	$168.83	12.294%	$189.586	$189.59	$189.60	$189.60
Purchase #5	$95.31	8.545%	$103.4542	$103.45	$103.45	$103.50
Purchase #6	$190.74	10.823%	$211.3838	$211.38	$211.40	$211.40
Purchase #7	$117.92	9.663%	$129.3146	$129.31	$129.30	$129.30
7 purchase totals =	$1,001.77		$1,092.8959	$1,092.89	$1,092.90	$1,092.90