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	$174.74	9.833%	$191.9222	$191.92	$191.90	$191.90
Purchase #2	$77.37	10.674%	$85.6285	$85.63	$85.65	$85.60
Purchase #3	$168.43	10.207%	$185.6217	$185.62	$185.60	$185.60
Purchase #4	$183.65	4.120%	$191.2164	$191.22	$191.20	$191.20
Purchase #5	$153.33	9.253%	$167.5176	$167.52	$167.50	$167.50
Purchase #6	$81.87	4.311%	$85.3994	$85.40	$85.40	$85.40
Purchase #7	$233.55	5.577%	$246.5751	$246.58	$246.60	$246.60
7 purchase totals =	$1,072.94		$1,153.8809	$1,153.89	$1,153.85	$1,153.80