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	$65.33	10.561%	$72.2295	$72.23	$72.25	$72.20
Purchase #2	$172.34	8.354%	$186.7373	$186.74	$186.75	$186.70
Purchase #3	$217.39	5.705%	$229.7921	$229.79	$229.80	$229.80
Purchase #4	$11.74	10.150%	$12.9316	$12.93	$12.95	$12.90
Purchase #5	$42.86	5.333%	$45.1457	$45.15	$45.15	$45.10
Purchase #6	$236.39	11.387%	$263.3077	$263.31	$263.30	$263.30
Purchase #7	$32.46	12.207%	$36.4224	$36.42	$36.40	$36.40
7 purchase totals =	$778.51		$846.5663	$846.57	$846.60	$846.40