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	$129.35	3.300%	$133.6186	$133.62	$133.60	$133.60
Purchase #2	$164.38	4.824%	$172.3097	$172.31	$172.30	$172.30
Purchase #3	$245.41	9.382%	$268.4344	$268.43	$268.45	$268.40
Purchase #4	$131.65	11.115%	$146.2829	$146.28	$146.30	$146.30
Purchase #5	$221.28	7.440%	$237.7432	$237.74	$237.75	$237.70
Purchase #6	$73.64	13.610%	$83.6624	$83.66	$83.65	$83.70
Purchase #7	$182.53	7.588%	$196.3804	$196.38	$196.40	$196.40
7 purchase totals =	$1,148.24		$1,238.4316	$1,238.42	$1,238.45	$1,238.40