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	$179.73	6.530%	$191.4664	$191.47	$191.45	$191.50
Purchase #2	$30.95	6.805%	$33.0561	$33.06	$33.05	$33.10
Purchase #3	$11.65	6.250%	$12.3781	$12.38	$12.40	$12.40
Purchase #4	$19.50	4.308%	$20.3401	$20.34	$20.35	$20.30
Purchase #5	$150.37	9.647%	$164.8762	$164.88	$164.90	$164.90
Purchase #6	$218.62	3.251%	$225.7273	$225.73	$225.75	$225.70
Purchase #7	$59.77	4.693%	$62.575	$62.58	$62.60	$62.60
7 purchase totals =	$670.59		$710.4192	$710.44	$710.50	$710.50