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	$201.44	6.641%	$214.8176	$214.82	$214.80	$214.80
Purchase #2	$106.67	4.359%	$111.3197	$111.32	$111.30	$111.30
Purchase #3	$74.92	4.438%	$78.2449	$78.24	$78.25	$78.20
Purchase #4	$74.60	11.637%	$83.2812	$83.28	$83.30	$83.30
Purchase #5	$172.57	7.479%	$185.4765	$185.48	$185.50	$185.50
Purchase #6	$20.31	8.318%	$21.9994	$22.00	$22.00	$22.00
Purchase #7	$94.90	12.506%	$106.7682	$106.77	$106.75	$106.80
7 purchase totals =	$745.41		$801.9075	$801.91	$801.90	$801.90