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	$245.26	9.404%	$268.3243	$268.32	$268.30	$268.30
Purchase #2	$238.30	3.359%	$246.3045	$246.30	$246.30	$246.30
Purchase #3	$184.38	6.829%	$196.9713	$196.97	$196.95	$197.00
Purchase #4	$217.80	3.453%	$225.3206	$225.32	$225.30	$225.30
Purchase #5	$196.48	13.142%	$222.3014	$222.30	$222.30	$222.30
Purchase #6	$143.35	7.310%	$153.8289	$153.83	$153.85	$153.80
Purchase #7	$167.44	11.420%	$186.5616	$186.56	$186.55	$186.60
7 purchase totals =	$1,393.01		$1,499.6126	$1,499.60	$1,499.55	$1,499.60