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	$227.57	9.642%	$249.5123	$249.51	$249.50	$249.50
Purchase #2	$19.32	6.143%	$20.5068	$20.51	$20.50	$20.50
Purchase #3	$165.98	4.155%	$172.8765	$172.88	$172.90	$172.90
Purchase #4	$108.71	6.406%	$115.674	$115.67	$115.65	$115.70
Purchase #5	$89.34	12.174%	$100.2163	$100.22	$100.20	$100.20
Purchase #6	$205.81	11.268%	$229.0007	$229.00	$229.00	$229.00
Purchase #7	$146.49	4.144%	$152.5605	$152.56	$152.55	$152.60
7 purchase totals =	$963.22		$1,040.3471	$1,040.35	$1,040.30	$1,040.40