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	$154.41	7.194%	$165.5183	$165.52	$165.50	$165.50
Purchase #2	$151.39	5.194%	$159.2532	$159.25	$159.25	$159.30
Purchase #3	$14.87	7.541%	$15.9913	$15.99	$16.00	$16.00
Purchase #4	$245.64	7.426%	$263.8812	$263.88	$263.90	$263.90
Purchase #5	$198.26	4.855%	$207.8855	$207.89	$207.90	$207.90
Purchase #6	$96.45	13.385%	$109.3598	$109.36	$109.35	$109.40
Purchase #7	$76.59	4.651%	$80.1522	$80.15	$80.15	$80.20
7 purchase totals =	$937.61		$1,002.0415	$1,002.04	$1,002.05	$1,002.20