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	$96.57	9.229%	$105.4824	$105.48	$105.50	$105.50
Purchase #2	$37.82	7.341%	$40.5964	$40.60	$40.60	$40.60
Purchase #3	$45.65	3.644%	$47.3135	$47.31	$47.30	$47.30
Purchase #4	$96.79	10.660%	$107.1078	$107.11	$107.10	$107.10
Purchase #5	$159.49	8.185%	$172.5443	$172.54	$172.55	$172.50
Purchase #6	$155.99	6.370%	$165.9266	$165.93	$165.95	$165.90
Purchase #7	$168.80	9.593%	$184.993	$184.99	$185.00	$185.00
7 purchase totals =	$761.11		$823.9640	$823.96	$824.00	$823.90