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	$219.32	8.363%	$237.6617	$237.66	$237.65	$237.70
Purchase #2	$248.93	10.418%	$274.8635	$274.86	$274.85	$274.90
Purchase #3	$148.46	5.500%	$156.6253	$156.63	$156.65	$156.60
Purchase #4	$114.67	8.148%	$124.0133	$124.01	$124.00	$124.00
Purchase #5	$55.31	8.219%	$59.8559	$59.86	$59.85	$59.90
Purchase #6	$216.95	7.507%	$233.2364	$233.24	$233.25	$233.20
Purchase #7	$240.65	5.781%	$254.562	$254.56	$254.55	$254.60
7 purchase totals =	$1,244.29		$1,340.8181	$1,340.82	$1,340.80	$1,340.90