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	$98.34	3.559%	$101.8399	$101.84	$101.85	$101.80
Purchase #2	$114.94	3.405%	$118.8537	$118.85	$118.85	$118.90
Purchase #3	$43.87	3.370%	$45.3484	$45.35	$45.35	$45.30
Purchase #4	$45.94	11.599%	$51.2686	$51.27	$51.25	$51.30
Purchase #5	$148.89	5.111%	$156.4998	$156.50	$156.50	$156.50
Purchase #6	$137.41	9.673%	$150.7017	$150.70	$150.70	$150.70
Purchase #7	$146.80	7.609%	$157.97	$157.97	$157.95	$158.00
7 purchase totals =	$736.19		$782.4821	$782.48	$782.45	$782.50