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	$169.32	12.829%	$191.0421	$191.04	$191.05	$191.00
Purchase #2	$223.71	11.648%	$249.7677	$249.77	$249.75	$249.80
Purchase #3	$133.55	9.644%	$146.4296	$146.43	$146.45	$146.40
Purchase #4	$241.87	8.739%	$263.007	$263.01	$263.00	$263.00
Purchase #5	$95.59	4.532%	$99.9221	$99.92	$99.90	$99.90
Purchase #6	$211.52	3.832%	$219.6254	$219.63	$219.65	$219.60
Purchase #7	$99.54	13.562%	$113.0396	$113.04	$113.05	$113.00
7 purchase totals =	$1,175.10		$1,282.8335	$1,282.84	$1,282.85	$1,282.70