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	$70.67	4.825%	$74.0798	$74.08	$74.10	$74.10
Purchase #2	$74.66	10.687%	$82.6389	$82.64	$82.65	$82.60
Purchase #3	$206.50	4.540%	$215.8751	$215.88	$215.90	$215.90
Purchase #4	$28.95	8.439%	$31.3931	$31.39	$31.40	$31.40
Purchase #5	$158.30	10.618%	$175.1083	$175.11	$175.10	$175.10
Purchase #6	$223.41	4.443%	$233.3361	$233.34	$233.35	$233.30
Purchase #7	$221.56	12.477%	$249.204	$249.20	$249.20	$249.20
7 purchase totals =	$984.05		$1,061.6353	$1,061.64	$1,061.70	$1,061.60