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	$56.88	7.513%	$61.1534	$61.15	$61.15	$61.20
Purchase #2	$149.66	13.276%	$169.5289	$169.53	$169.55	$169.50
Purchase #3	$35.34	5.615%	$37.3243	$37.32	$37.30	$37.30
Purchase #4	$82.38	4.576%	$86.1497	$86.15	$86.15	$86.10
Purchase #5	$70.67	10.285%	$77.9384	$77.94	$77.95	$77.90
Purchase #6	$245.51	10.363%	$270.9522	$270.95	$270.95	$271.00
Purchase #7	$210.89	6.613%	$224.8362	$224.84	$224.85	$224.80
7 purchase totals =	$851.33		$927.8831	$927.88	$927.90	$927.80