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	$108.96	13.557%	$123.7317	$123.73	$123.75	$123.70
Purchase #2	$146.84	3.815%	$152.4419	$152.44	$152.45	$152.40
Purchase #3	$71.60	9.440%	$78.359	$78.36	$78.35	$78.40
Purchase #4	$189.37	11.871%	$211.8501	$211.85	$211.85	$211.90
Purchase #5	$30.90	13.613%	$35.1064	$35.11	$35.10	$35.10
Purchase #6	$28.39	13.527%	$32.2303	$32.23	$32.25	$32.20
Purchase #7	$17.64	7.193%	$18.9088	$18.91	$18.90	$18.90
7 purchase totals =	$593.70		$652.6282	$652.63	$652.65	$652.60