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	$52.51	3.389%	$54.2896	$54.29	$54.30	$54.30
Purchase #2	$68.32	6.533%	$72.7833	$72.78	$72.80	$72.80
Purchase #3	$154.27	7.170%	$165.3312	$165.33	$165.35	$165.30
Purchase #4	$109.77	3.498%	$113.6098	$113.61	$113.60	$113.60
Purchase #5	$206.32	6.492%	$219.7143	$219.71	$219.70	$219.70
Purchase #6	$53.71	13.569%	$60.9979	$61.00	$61.00	$61.00
Purchase #7	$141.92	11.768%	$158.6211	$158.62	$158.60	$158.60
7 purchase totals =	$786.82		$845.3472	$845.34	$845.35	$845.30