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	$168.40	3.766%	$174.7419	$174.74	$174.75	$174.70
Purchase #2	$34.46	12.545%	$38.783	$38.78	$38.80	$38.80
Purchase #3	$30.37	10.404%	$33.5297	$33.53	$33.55	$33.50
Purchase #4	$159.54	4.740%	$167.1022	$167.10	$167.10	$167.10
Purchase #5	$169.36	12.751%	$190.9551	$190.96	$190.95	$191.00
Purchase #6	$11.27	8.678%	$12.248	$12.25	$12.25	$12.20
Purchase #7	$166.45	11.688%	$185.9047	$185.90	$185.90	$185.90
7 purchase totals =	$739.85		$803.2646	$803.26	$803.30	$803.20