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	$151.80	3.577%	$157.2299	$157.23	$157.25	$157.20
Purchase #2	$58.76	7.673%	$63.2687	$63.27	$63.25	$63.30
Purchase #3	$94.62	6.300%	$100.5811	$100.58	$100.60	$100.60
Purchase #4	$214.86	6.162%	$228.0997	$228.10	$228.10	$228.10
Purchase #5	$190.88	11.642%	$213.1022	$213.10	$213.10	$213.10
Purchase #6	$179.77	9.108%	$196.1435	$196.14	$196.15	$196.10
Purchase #7	$99.98	13.586%	$113.5633	$113.56	$113.55	$113.60
7 purchase totals =	$990.67		$1,071.9884	$1,071.98	$1,072.00	$1,072.00