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	$220.69	10.303%	$243.4277	$243.43	$243.45	$243.40
Purchase #2	$148.27	13.549%	$168.3591	$168.36	$168.35	$168.40
Purchase #3	$166.36	8.523%	$180.5389	$180.54	$180.55	$180.50
Purchase #4	$96.39	7.512%	$103.6308	$103.63	$103.65	$103.60
Purchase #5	$154.58	8.619%	$167.9033	$167.90	$167.90	$167.90
Purchase #6	$60.98	9.489%	$66.7664	$66.77	$66.75	$66.80
Purchase #7	$101.34	9.619%	$111.0879	$111.09	$111.10	$111.10
7 purchase totals =	$948.61		$1,041.7141	$1,041.72	$1,041.75	$1,041.70