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	$242.90	11.427%	$270.6562	$270.66	$270.65	$270.70
Purchase #2	$6.70	6.129%	$7.1106	$7.11	$7.10	$7.10
Purchase #3	$126.34	4.211%	$131.6602	$131.66	$131.65	$131.70
Purchase #4	$156.51	6.419%	$166.5564	$166.56	$166.55	$166.60
Purchase #5	$184.27	4.679%	$192.892	$192.89	$192.90	$192.90
Purchase #6	$145.28	7.209%	$155.7532	$155.75	$155.75	$155.80
Purchase #7	$114.31	8.372%	$123.88	$123.88	$123.90	$123.90
7 purchase totals =	$976.31		$1,048.5086	$1,048.51	$1,048.50	$1,048.70