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	$178.41	11.830%	$199.5159	$199.52	$199.50	$199.50
Purchase #2	$225.27	4.531%	$235.477	$235.48	$235.50	$235.50
Purchase #3	$94.36	3.551%	$97.7107	$97.71	$97.70	$97.70
Purchase #4	$102.70	6.544%	$109.4207	$109.42	$109.40	$109.40
Purchase #5	$89.53	3.482%	$92.6474	$92.65	$92.65	$92.60
Purchase #6	$193.63	3.437%	$200.2851	$200.29	$200.30	$200.30
Purchase #7	$61.39	6.750%	$65.5338	$65.53	$65.55	$65.50
7 purchase totals =	$945.29		$1,000.5906	$1,000.60	$1,000.60	$1,000.50