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	$86.85	6.670%	$92.6429	$92.64	$92.65	$92.60
Purchase #2	$32.74	3.156%	$33.7733	$33.77	$33.75	$33.80
Purchase #3	$62.43	13.795%	$71.0422	$71.04	$71.05	$71.00
Purchase #4	$141.92	13.215%	$160.6747	$160.67	$160.65	$160.70
Purchase #5	$29.56	5.145%	$31.0809	$31.08	$31.10	$31.10
Purchase #6	$209.92	5.346%	$221.1423	$221.14	$221.15	$221.10
Purchase #7	$224.73	6.322%	$238.9374	$238.94	$238.95	$238.90
7 purchase totals =	$788.15		$849.2937	$849.28	$849.30	$849.20