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	$233.65	4.529%	$244.232	$244.23	$244.25	$244.20
Purchase #2	$153.41	5.292%	$161.5285	$161.53	$161.55	$161.50
Purchase #3	$183.56	9.219%	$200.4824	$200.48	$200.50	$200.50
Purchase #4	$33.26	10.438%	$36.7317	$36.73	$36.75	$36.70
Purchase #5	$152.31	6.674%	$162.4752	$162.48	$162.50	$162.50
Purchase #6	$66.32	3.117%	$68.3872	$68.39	$68.40	$68.40
Purchase #7	$173.76	7.802%	$187.3168	$187.32	$187.30	$187.30
7 purchase totals =	$996.27		$1,061.1538	$1,061.16	$1,061.25	$1,061.10