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	$208.45	5.583%	$220.0878	$220.09	$220.10	$220.10
Purchase #2	$128.61	13.450%	$145.908	$145.91	$145.90	$145.90
Purchase #3	$118.43	11.351%	$131.873	$131.87	$131.85	$131.90
Purchase #4	$213.29	5.688%	$225.4219	$225.42	$225.40	$225.40
Purchase #5	$162.79	13.251%	$184.3613	$184.36	$184.35	$184.40
Purchase #6	$104.45	4.728%	$109.3884	$109.39	$109.40	$109.40
Purchase #7	$145.32	13.818%	$165.4003	$165.40	$165.40	$165.40
7 purchase totals =	$1,081.34		$1,182.4407	$1,182.44	$1,182.40	$1,182.50