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	$191.89	6.493%	$204.3494	$204.35	$204.35	$204.30
Purchase #2	$66.46	4.231%	$69.2719	$69.27	$69.25	$69.30
Purchase #3	$40.33	3.819%	$41.8702	$41.87	$41.85	$41.90
Purchase #4	$96.68	7.404%	$103.8382	$103.84	$103.85	$103.80
Purchase #5	$153.54	7.403%	$164.9066	$164.91	$164.90	$164.90
Purchase #6	$160.89	11.582%	$179.5243	$179.52	$179.50	$179.50
Purchase #7	$209.92	3.569%	$217.412	$217.41	$217.40	$217.40
7 purchase totals =	$919.71		$981.1726	$981.17	$981.10	$981.10