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	$175.49	9.846%	$192.7687	$192.77	$192.75	$192.80
Purchase #2	$231.56	10.226%	$255.2393	$255.24	$255.25	$255.20
Purchase #3	$150.66	7.427%	$161.8495	$161.85	$161.85	$161.80
Purchase #4	$99.74	4.253%	$103.9819	$103.98	$104.00	$104.00
Purchase #5	$130.80	9.137%	$142.7512	$142.75	$142.75	$142.80
Purchase #6	$112.90	9.539%	$123.6695	$123.67	$123.65	$123.70
Purchase #7	$59.49	9.133%	$64.9232	$64.92	$64.90	$64.90
7 purchase totals =	$960.64		$1,045.1833	$1,045.18	$1,045.15	$1,045.20