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	$127.46	3.148%	$131.4724	$131.47	$131.45	$131.50
Purchase #2	$182.34	11.264%	$202.8788	$202.88	$202.90	$202.90
Purchase #3	$33.58	13.702%	$38.1811	$38.18	$38.20	$38.20
Purchase #4	$127.46	3.331%	$131.7057	$131.71	$131.70	$131.70
Purchase #5	$92.89	5.515%	$98.0129	$98.01	$98.00	$98.00
Purchase #6	$118.56	5.146%	$124.6611	$124.66	$124.65	$124.70
Purchase #7	$136.92	10.617%	$151.4568	$151.46	$151.45	$151.50
7 purchase totals =	$819.21		$878.3688	$878.37	$878.35	$878.50