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	$204.75	5.411%	$215.829	$215.83	$215.85	$215.80
Purchase #2	$156.25	3.827%	$162.2297	$162.23	$162.25	$162.20
Purchase #3	$104.26	6.736%	$111.283	$111.28	$111.30	$111.30
Purchase #4	$39.94	8.515%	$43.3409	$43.34	$43.35	$43.30
Purchase #5	$55.66	7.696%	$59.9436	$59.94	$59.95	$59.90
Purchase #6	$109.72	7.188%	$117.6067	$117.61	$117.60	$117.60
Purchase #7	$220.57	10.168%	$242.9976	$243.00	$243.00	$243.00
7 purchase totals =	$891.15		$953.2305	$953.23	$953.30	$953.10