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	$160.61	4.844%	$168.3899	$168.39	$168.40	$168.40
Purchase #2	$177.48	9.855%	$194.9707	$194.97	$194.95	$195.00
Purchase #3	$179.87	6.346%	$191.2846	$191.28	$191.30	$191.30
Purchase #4	$137.79	9.789%	$151.2783	$151.28	$151.30	$151.30
Purchase #5	$250.32	3.629%	$259.4041	$259.40	$259.40	$259.40
Purchase #6	$37.45	7.831%	$40.3827	$40.38	$40.40	$40.40
Purchase #7	$157.61	6.145%	$167.2951	$167.30	$167.30	$167.30
7 purchase totals =	$1,101.13		$1,173.0054	$1,173.00	$1,173.05	$1,173.10