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	$192.84	7.661%	$207.6135	$207.61	$207.60	$207.60
Purchase #2	$83.53	9.216%	$91.2281	$91.23	$91.25	$91.20
Purchase #3	$47.77	5.468%	$50.3821	$50.38	$50.40	$50.40
Purchase #4	$12.51	10.282%	$13.7963	$13.80	$13.80	$13.80
Purchase #5	$166.37	11.468%	$185.4493	$185.45	$185.45	$185.40
Purchase #6	$245.31	4.184%	$255.5738	$255.57	$255.55	$255.60
Purchase #7	$67.69	13.648%	$76.9283	$76.93	$76.95	$76.90
7 purchase totals =	$816.02		$880.9714	$880.97	$881.00	$880.90