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	$222.56	13.797%	$253.2666	$253.27	$253.25	$253.30
Purchase #2	$171.63	11.494%	$191.3572	$191.36	$191.35	$191.40
Purchase #3	$230.94	4.811%	$242.0505	$242.05	$242.05	$242.10
Purchase #4	$115.74	6.508%	$123.2724	$123.27	$123.25	$123.30
Purchase #5	$85.95	6.312%	$91.3752	$91.38	$91.40	$91.40
Purchase #6	$49.37	3.858%	$51.2747	$51.27	$51.25	$51.30
Purchase #7	$165.37	3.274%	$170.7842	$170.78	$170.80	$170.80
7 purchase totals =	$1,041.56		$1,123.3808	$1,123.38	$1,123.35	$1,123.60