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	$33.77	6.365%	$35.9195	$35.92	$35.90	$35.90
Purchase #2	$185.40	12.254%	$208.1189	$208.12	$208.10	$208.10
Purchase #3	$42.28	3.566%	$43.7877	$43.79	$43.80	$43.80
Purchase #4	$175.88	6.440%	$187.2067	$187.21	$187.20	$187.20
Purchase #5	$146.56	5.872%	$155.166	$155.17	$155.15	$155.20
Purchase #6	$169.56	12.396%	$190.5787	$190.58	$190.60	$190.60
Purchase #7	$194.60	8.648%	$211.429	$211.43	$211.45	$211.40
7 purchase totals =	$948.05		$1,032.2065	$1,032.22	$1,032.20	$1,032.20