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	$72.67	7.465%	$78.0948	$78.09	$78.10	$78.10
Purchase #2	$94.84	4.795%	$99.3876	$99.39	$99.40	$99.40
Purchase #3	$56.54	4.561%	$59.1188	$59.12	$59.10	$59.10
Purchase #4	$226.88	7.709%	$244.3702	$244.37	$244.35	$244.40
Purchase #5	$195.70	12.511%	$220.184	$220.18	$220.20	$220.20
Purchase #6	$9.88	6.102%	$10.4829	$10.48	$10.50	$10.50
Purchase #7	$65.79	13.430%	$74.6256	$74.63	$74.65	$74.60
7 purchase totals =	$722.30		$786.2639	$786.26	$786.30	$786.30