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	$132.81	6.118%	$140.9353	$140.94	$140.95	$140.90
Purchase #2	$11.86	3.853%	$12.317	$12.32	$12.30	$12.30
Purchase #3	$157.26	11.749%	$175.7365	$175.74	$175.75	$175.70
Purchase #4	$168.39	9.623%	$184.5942	$184.59	$184.60	$184.60
Purchase #5	$99.46	11.722%	$111.1187	$111.12	$111.10	$111.10
Purchase #6	$110.81	4.159%	$115.4186	$115.42	$115.40	$115.40
Purchase #7	$234.61	12.430%	$263.772	$263.77	$263.75	$263.80
7 purchase totals =	$915.20		$1,003.8923	$1,003.90	$1,003.85	$1,003.80