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	$63.98	5.449%	$67.4663	$67.47	$67.45	$67.50
Purchase #2	$244.61	8.648%	$265.7639	$265.76	$265.75	$265.80
Purchase #3	$147.90	3.620%	$153.254	$153.25	$153.25	$153.30
Purchase #4	$126.82	10.147%	$139.6884	$139.69	$139.70	$139.70
Purchase #5	$210.28	5.692%	$222.2491	$222.25	$222.25	$222.20
Purchase #6	$224.97	4.282%	$234.6032	$234.60	$234.60	$234.60
Purchase #7	$18.77	9.586%	$20.5693	$20.57	$20.55	$20.60
7 purchase totals =	$1,037.33		$1,103.5942	$1,103.59	$1,103.55	$1,103.70