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	$94.65	11.262%	$105.3095	$105.31	$105.30	$105.30
Purchase #2	$187.98	9.357%	$205.5693	$205.57	$205.55	$205.60
Purchase #3	$139.90	8.566%	$151.8838	$151.88	$151.90	$151.90
Purchase #4	$221.95	6.266%	$235.8574	$235.86	$235.85	$235.90
Purchase #5	$250.34	7.672%	$269.5461	$269.55	$269.55	$269.50
Purchase #6	$151.75	10.197%	$167.2239	$167.22	$167.20	$167.20
Purchase #7	$15.88	10.489%	$17.5457	$17.55	$17.55	$17.50
7 purchase totals =	$1,062.45		$1,152.9357	$1,152.94	$1,152.90	$1,152.90