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	$210.36	4.169%	$219.1299	$219.13	$219.15	$219.10
Purchase #2	$33.72	6.669%	$35.9688	$35.97	$35.95	$36.00
Purchase #3	$86.71	3.721%	$89.9365	$89.94	$89.95	$89.90
Purchase #4	$246.67	7.128%	$264.2526	$264.25	$264.25	$264.30
Purchase #5	$87.90	3.112%	$90.6354	$90.64	$90.65	$90.60
Purchase #6	$98.48	3.218%	$101.6491	$101.65	$101.65	$101.60
Purchase #7	$147.87	5.237%	$155.614	$155.61	$155.60	$155.60
7 purchase totals =	$911.71		$957.1863	$957.19	$957.20	$957.10