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	$33.35	6.263%	$35.4387	$35.44	$35.45	$35.40
Purchase #2	$17.99	12.253%	$20.1943	$20.19	$20.20	$20.20
Purchase #3	$33.77	10.731%	$37.3939	$37.39	$37.40	$37.40
Purchase #4	$11.78	3.419%	$12.1828	$12.18	$12.20	$12.20
Purchase #5	$200.42	7.558%	$215.5677	$215.57	$215.55	$215.60
Purchase #6	$52.66	12.343%	$59.1598	$59.16	$59.15	$59.20
Purchase #7	$178.59	8.769%	$194.2506	$194.25	$194.25	$194.30
7 purchase totals =	$528.56		$574.1878	$574.18	$574.20	$574.30