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	$8.42	5.680%	$8.8983	$8.90	$8.90	$8.90
Purchase #2	$96.27	4.130%	$100.246	$100.25	$100.25	$100.20
Purchase #3	$42.91	7.483%	$46.121	$46.12	$46.10	$46.10
Purchase #4	$246.72	11.723%	$275.643	$275.64	$275.65	$275.60
Purchase #5	$250.65	12.756%	$282.6229	$282.62	$282.60	$282.60
Purchase #6	$215.37	11.139%	$239.3601	$239.36	$239.35	$239.40
Purchase #7	$174.73	9.644%	$191.581	$191.58	$191.60	$191.60
7 purchase totals =	$1,035.07		$1,144.4723	$1,144.47	$1,144.45	$1,144.40