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	$69.80	3.575%	$72.2954	$72.30	$72.30	$72.30
Purchase #2	$161.42	3.489%	$167.0519	$167.05	$167.05	$167.10
Purchase #3	$69.44	4.276%	$72.4093	$72.41	$72.40	$72.40
Purchase #4	$128.31	9.521%	$140.5264	$140.53	$140.55	$140.50
Purchase #5	$71.72	12.476%	$80.6678	$80.67	$80.65	$80.70
Purchase #6	$23.43	8.164%	$25.3428	$25.34	$25.35	$25.30
Purchase #7	$204.25	6.646%	$217.8245	$217.82	$217.80	$217.80
7 purchase totals =	$728.37		$776.1181	$776.12	$776.10	$776.10