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	$207.99	9.302%	$227.3372	$227.34	$227.35	$227.30
Purchase #2	$72.91	5.870%	$77.1898	$77.19	$77.20	$77.20
Purchase #3	$74.83	11.616%	$83.5223	$83.52	$83.50	$83.50
Purchase #4	$146.48	12.844%	$165.2939	$165.29	$165.30	$165.30
Purchase #5	$145.93	5.752%	$154.3239	$154.32	$154.30	$154.30
Purchase #6	$56.55	4.673%	$59.1926	$59.19	$59.20	$59.20
Purchase #7	$241.72	11.164%	$268.7056	$268.71	$268.70	$268.70
7 purchase totals =	$946.41		$1,035.5653	$1,035.56	$1,035.55	$1,035.50