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	$129.56	3.158%	$133.6515	$133.65	$133.65	$133.70
Purchase #2	$103.71	4.782%	$108.6694	$108.67	$108.65	$108.70
Purchase #3	$82.76	11.183%	$92.0151	$92.02	$92.00	$92.00
Purchase #4	$18.31	5.191%	$19.2605	$19.26	$19.25	$19.30
Purchase #5	$70.86	3.720%	$73.496	$73.50	$73.50	$73.50
Purchase #6	$146.29	11.157%	$162.6116	$162.61	$162.60	$162.60
Purchase #7	$184.81	6.283%	$196.4216	$196.42	$196.40	$196.40
7 purchase totals =	$736.30		$786.1257	$786.13	$786.05	$786.20