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	$162.68	3.199%	$167.8841	$167.88	$167.90	$167.90
Purchase #2	$167.29	3.315%	$172.8357	$172.84	$172.85	$172.80
Purchase #3	$14.48	12.763%	$16.3281	$16.33	$16.35	$16.30
Purchase #4	$113.32	13.716%	$128.863	$128.86	$128.85	$128.90
Purchase #5	$250.32	5.873%	$265.0213	$265.02	$265.00	$265.00
Purchase #6	$7.56	4.683%	$7.914	$7.91	$7.90	$7.90
Purchase #7	$226.61	8.144%	$245.0651	$245.07	$245.05	$245.10
7 purchase totals =	$942.26		$1,003.9113	$1,003.91	$1,003.90	$1,003.90