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	$145.62	13.750%	$165.6428	$165.64	$165.65	$165.60
Purchase #2	$186.45	7.476%	$200.389	$200.39	$200.40	$200.40
Purchase #3	$172.48	12.380%	$193.833	$193.83	$193.85	$193.80
Purchase #4	$205.30	5.860%	$217.3306	$217.33	$217.35	$217.30
Purchase #5	$56.62	6.789%	$60.4639	$60.46	$60.45	$60.50
Purchase #6	$96.29	3.817%	$99.9654	$99.97	$99.95	$100.00
Purchase #7	$82.88	3.207%	$85.538	$85.54	$85.55	$85.50
7 purchase totals =	$945.64		$1,023.1627	$1,023.16	$1,023.20	$1,023.10