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	$221.84	6.535%	$236.3372	$236.34	$236.35	$236.30
Purchase #2	$5.72	13.490%	$6.4916	$6.49	$6.50	$6.50
Purchase #3	$104.43	6.804%	$111.5354	$111.54	$111.55	$111.50
Purchase #4	$94.55	6.524%	$100.7184	$100.72	$100.70	$100.70
Purchase #5	$113.50	8.489%	$123.135	$123.14	$123.15	$123.10
Purchase #6	$173.97	12.747%	$196.146	$196.15	$196.15	$196.10
Purchase #7	$69.73	10.114%	$76.7825	$76.78	$76.80	$76.80
7 purchase totals =	$783.74		$851.1461	$851.16	$851.20	$851.00