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	$211.89	12.636%	$238.6644	$238.66	$238.65	$238.70
Purchase #2	$132.78	6.523%	$141.4412	$141.44	$141.45	$141.40
Purchase #3	$18.41	10.571%	$20.3561	$20.36	$20.35	$20.40
Purchase #4	$167.66	9.821%	$184.1259	$184.13	$184.15	$184.10
Purchase #5	$168.28	10.525%	$185.9915	$185.99	$186.00	$186.00
Purchase #6	$181.41	6.651%	$193.4756	$193.48	$193.50	$193.50
Purchase #7	$43.91	3.297%	$45.3577	$45.36	$45.35	$45.40
7 purchase totals =	$924.34		$1,009.4124	$1,009.42	$1,009.45	$1,009.50