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	$64.46	12.133%	$72.2809	$72.28	$72.30	$72.30
Purchase #2	$223.65	13.303%	$253.4022	$253.40	$253.40	$253.40
Purchase #3	$110.35	6.812%	$117.867	$117.87	$117.85	$117.90
Purchase #4	$110.89	11.207%	$123.3174	$123.32	$123.30	$123.30
Purchase #5	$90.62	4.824%	$94.9915	$94.99	$95.00	$95.00
Purchase #6	$15.34	12.598%	$17.2725	$17.27	$17.25	$17.30
Purchase #7	$68.46	6.140%	$72.6634	$72.66	$72.65	$72.70
7 purchase totals =	$683.77		$751.7949	$751.79	$751.75	$751.90