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	$245.79	7.249%	$263.6073	$263.61	$263.60	$263.60
Purchase #2	$14.50	11.154%	$16.1173	$16.12	$16.10	$16.10
Purchase #3	$57.41	3.355%	$59.3361	$59.34	$59.35	$59.30
Purchase #4	$229.45	11.274%	$255.3182	$255.32	$255.30	$255.30
Purchase #5	$145.69	11.274%	$162.1151	$162.12	$162.10	$162.10
Purchase #6	$81.52	9.125%	$88.9587	$88.96	$88.95	$89.00
Purchase #7	$143.69	4.687%	$150.4248	$150.42	$150.40	$150.40
7 purchase totals =	$918.05		$995.8775	$995.89	$995.80	$995.80