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	$85.92	12.734%	$96.8611	$96.86	$96.85	$96.90
Purchase #2	$237.59	10.724%	$263.0692	$263.07	$263.05	$263.10
Purchase #3	$151.88	11.163%	$168.8344	$168.83	$168.85	$168.80
Purchase #4	$134.85	8.735%	$146.6291	$146.63	$146.65	$146.60
Purchase #5	$163.51	5.558%	$172.5979	$172.60	$172.60	$172.60
Purchase #6	$50.70	5.590%	$53.5341	$53.53	$53.55	$53.50
Purchase #7	$119.74	9.655%	$131.3009	$131.30	$131.30	$131.30
7 purchase totals =	$944.19		$1,032.8267	$1,032.82	$1,032.85	$1,032.80