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	$121.38	5.164%	$127.6481	$127.65	$127.65	$127.60
Purchase #2	$234.91	12.458%	$264.1751	$264.18	$264.20	$264.20
Purchase #3	$65.25	10.777%	$72.282	$72.28	$72.30	$72.30
Purchase #4	$125.74	11.512%	$140.2152	$140.22	$140.20	$140.20
Purchase #5	$25.73	10.645%	$28.469	$28.47	$28.45	$28.50
Purchase #6	$198.96	11.160%	$221.1639	$221.16	$221.15	$221.20
Purchase #7	$165.89	4.208%	$172.8707	$172.87	$172.85	$172.90
7 purchase totals =	$937.86		$1,026.8240	$1,026.83	$1,026.80	$1,026.90