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	$60.75	6.633%	$64.7795	$64.78	$64.80	$64.80
Purchase #2	$143.56	6.460%	$152.834	$152.83	$152.85	$152.80
Purchase #3	$41.30	3.517%	$42.7525	$42.75	$42.75	$42.80
Purchase #4	$238.58	6.365%	$253.7656	$253.77	$253.75	$253.80
Purchase #5	$214.49	4.851%	$224.8949	$224.89	$224.90	$224.90
Purchase #6	$223.34	12.352%	$250.927	$250.93	$250.95	$250.90
Purchase #7	$173.79	5.756%	$183.7934	$183.79	$183.80	$183.80
7 purchase totals =	$1,095.81		$1,173.7469	$1,173.74	$1,173.80	$1,173.80