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	$209.32	6.649%	$223.2377	$223.24	$223.25	$223.20
Purchase #2	$229.32	6.520%	$244.2717	$244.27	$244.25	$244.30
Purchase #3	$102.57	10.241%	$113.0742	$113.07	$113.05	$113.10
Purchase #4	$67.91	13.603%	$77.1478	$77.15	$77.15	$77.10
Purchase #5	$41.41	9.727%	$45.438	$45.44	$45.45	$45.40
Purchase #6	$200.34	4.635%	$209.6258	$209.63	$209.65	$209.60
Purchase #7	$163.54	9.298%	$178.7459	$178.75	$178.75	$178.70
7 purchase totals =	$1,014.41		$1,091.5411	$1,091.55	$1,091.55	$1,091.40