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	$73.74	12.745%	$83.1382	$83.14	$83.15	$83.10
Purchase #2	$31.32	7.525%	$33.6768	$33.68	$33.70	$33.70
Purchase #3	$138.91	8.604%	$150.8618	$150.86	$150.85	$150.90
Purchase #4	$135.38	12.628%	$152.4758	$152.48	$152.50	$152.50
Purchase #5	$58.51	10.405%	$64.598	$64.60	$64.60	$64.60
Purchase #6	$146.96	13.357%	$166.5894	$166.59	$166.60	$166.60
Purchase #7	$51.35	5.581%	$54.2158	$54.22	$54.20	$54.20
7 purchase totals =	$636.17		$705.5558	$705.57	$705.60	$705.60