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	$147.46	13.839%	$167.867	$167.87	$167.85	$167.90
Purchase #2	$225.53	7.578%	$242.6207	$242.62	$242.60	$242.60
Purchase #3	$157.33	7.788%	$169.5829	$169.58	$169.60	$169.60
Purchase #4	$75.92	11.666%	$84.7768	$84.78	$84.80	$84.80
Purchase #5	$158.43	8.279%	$171.5464	$171.55	$171.55	$171.50
Purchase #6	$150.84	3.433%	$156.0183	$156.02	$156.00	$156.00
Purchase #7	$80.78	9.674%	$88.5947	$88.59	$88.60	$88.60
7 purchase totals =	$996.29		$1,081.0068	$1,081.01	$1,081.00	$1,081.00