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	$46.44	11.768%	$51.9051	$51.91	$51.90	$51.90
Purchase #2	$99.56	4.343%	$103.8839	$103.88	$103.90	$103.90
Purchase #3	$191.85	6.870%	$205.0301	$205.03	$205.05	$205.00
Purchase #4	$190.82	12.342%	$214.371	$214.37	$214.35	$214.40
Purchase #5	$134.52	5.295%	$141.6428	$141.64	$141.65	$141.60
Purchase #6	$116.30	7.444%	$124.9574	$124.96	$124.95	$125.00
Purchase #7	$218.78	11.518%	$243.9791	$243.98	$244.00	$244.00
7 purchase totals =	$998.27		$1,085.7694	$1,085.77	$1,085.80	$1,085.80