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	$31.31	4.118%	$32.5993	$32.60	$32.60	$32.60
Purchase #2	$123.69	11.121%	$137.4456	$137.45	$137.45	$137.40
Purchase #3	$141.92	6.338%	$150.9149	$150.91	$150.90	$150.90
Purchase #4	$103.63	11.425%	$115.4697	$115.47	$115.45	$115.50
Purchase #5	$80.74	13.444%	$91.5947	$91.59	$91.60	$91.60
Purchase #6	$136.97	6.384%	$145.7142	$145.71	$145.70	$145.70
Purchase #7	$29.89	13.519%	$33.9308	$33.93	$33.95	$33.90
7 purchase totals =	$648.15		$707.6692	$707.66	$707.65	$707.60