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	$91.77	10.196%	$101.1269	$101.13	$101.15	$101.10
Purchase #2	$171.65	6.241%	$182.3627	$182.36	$182.35	$182.40
Purchase #3	$174.49	6.574%	$185.961	$185.96	$185.95	$186.00
Purchase #4	$34.57	7.483%	$37.1569	$37.16	$37.15	$37.20
Purchase #5	$149.34	5.471%	$157.5104	$157.51	$157.50	$157.50
Purchase #6	$154.91	10.602%	$171.3336	$171.33	$171.35	$171.30
Purchase #7	$153.91	11.779%	$172.0391	$172.04	$172.05	$172.00
7 purchase totals =	$930.64		$1,007.4906	$1,007.49	$1,007.50	$1,007.50