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	$132.33	12.526%	$148.9057	$148.91	$148.90	$148.90
Purchase #2	$19.39	4.771%	$20.3151	$20.32	$20.30	$20.30
Purchase #3	$132.93	5.644%	$140.4326	$140.43	$140.45	$140.40
Purchase #4	$52.92	5.592%	$55.8793	$55.88	$55.90	$55.90
Purchase #5	$116.93	9.199%	$127.6864	$127.69	$127.70	$127.70
Purchase #6	$5.28	9.227%	$5.7672	$5.77	$5.75	$5.80
Purchase #7	$60.75	10.313%	$67.0151	$67.02	$67.00	$67.00
7 purchase totals =	$520.53		$566.0014	$566.02	$566.00	$566.00