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	$68.29	10.647%	$75.5608	$75.56	$75.55	$75.60
Purchase #2	$94.27	6.819%	$100.6983	$100.70	$100.70	$100.70
Purchase #3	$162.30	3.578%	$168.1071	$168.11	$168.10	$168.10
Purchase #4	$59.25	11.286%	$65.937	$65.94	$65.95	$65.90
Purchase #5	$104.92	7.112%	$112.3819	$112.38	$112.40	$112.40
Purchase #6	$216.78	10.492%	$239.5246	$239.52	$239.50	$239.50
Purchase #7	$146.82	3.470%	$151.9147	$151.91	$151.90	$151.90
7 purchase totals =	$852.63		$914.1244	$914.12	$914.10	$914.10