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	$147.28	11.463%	$164.1627	$164.16	$164.15	$164.20
Purchase #2	$30.72	9.328%	$33.5856	$33.59	$33.60	$33.60
Purchase #3	$59.83	8.206%	$64.7396	$64.74	$64.75	$64.70
Purchase #4	$22.94	12.824%	$25.8818	$25.88	$25.90	$25.90
Purchase #5	$149.96	11.405%	$167.0629	$167.06	$167.05	$167.10
Purchase #6	$227.56	13.718%	$258.7767	$258.78	$258.80	$258.80
Purchase #7	$152.71	3.565%	$158.1541	$158.15	$158.15	$158.20
7 purchase totals =	$791.00		$872.3634	$872.36	$872.40	$872.50