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	$200.77	11.714%	$224.2882	$224.29	$224.30	$224.30
Purchase #2	$194.98	8.593%	$211.7346	$211.73	$211.75	$211.70
Purchase #3	$19.85	3.187%	$20.4826	$20.48	$20.50	$20.50
Purchase #4	$60.31	6.610%	$64.2965	$64.30	$64.30	$64.30
Purchase #5	$69.33	3.555%	$71.7947	$71.79	$71.80	$71.80
Purchase #6	$186.85	5.396%	$196.9324	$196.93	$196.95	$196.90
Purchase #7	$84.60	5.391%	$89.1608	$89.16	$89.15	$89.20
7 purchase totals =	$816.69		$878.6898	$878.68	$878.75	$878.70