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	$155.30	10.350%	$171.3736	$171.37	$171.35	$171.40
Purchase #2	$184.88	5.355%	$194.7803	$194.78	$194.80	$194.80
Purchase #3	$126.55	5.117%	$133.0256	$133.03	$133.05	$133.00
Purchase #4	$220.59	4.611%	$230.7614	$230.76	$230.75	$230.80
Purchase #5	$71.96	6.340%	$76.5223	$76.52	$76.50	$76.50
Purchase #6	$94.29	11.588%	$105.2163	$105.22	$105.20	$105.20
Purchase #7	$136.91	11.266%	$152.3343	$152.33	$152.35	$152.30
7 purchase totals =	$990.48		$1,064.0138	$1,064.01	$1,064.00	$1,064.00