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	$79.46	7.431%	$85.3647	$85.36	$85.35	$85.40
Purchase #2	$198.42	11.494%	$221.2264	$221.23	$221.25	$221.20
Purchase #3	$101.46	5.275%	$106.812	$106.81	$106.80	$106.80
Purchase #4	$158.97	5.609%	$167.8866	$167.89	$167.90	$167.90
Purchase #5	$27.56	13.466%	$31.2712	$31.27	$31.25	$31.30
Purchase #6	$24.44	4.658%	$25.5784	$25.58	$25.60	$25.60
Purchase #7	$99.75	10.570%	$110.2936	$110.29	$110.30	$110.30
7 purchase totals =	$690.06		$748.4329	$748.43	$748.45	$748.50