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	$117.44	8.355%	$127.2521	$127.25	$127.25	$127.30
Purchase #2	$244.82	10.426%	$270.3449	$270.34	$270.35	$270.30
Purchase #3	$162.61	6.260%	$172.7894	$172.79	$172.80	$172.80
Purchase #4	$133.53	8.592%	$145.0029	$145.00	$145.00	$145.00
Purchase #5	$94.30	5.272%	$99.2715	$99.27	$99.25	$99.30
Purchase #6	$192.59	6.352%	$204.8233	$204.82	$204.80	$204.80
Purchase #7	$91.79	3.472%	$94.9769	$94.98	$95.00	$95.00
7 purchase totals =	$1,037.08		$1,114.4610	$1,114.45	$1,114.45	$1,114.50