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	$211.98	7.256%	$227.3613	$227.36	$227.35	$227.40
Purchase #2	$133.99	13.636%	$152.2609	$152.26	$152.25	$152.30
Purchase #3	$149.32	8.844%	$162.5259	$162.53	$162.55	$162.50
Purchase #4	$124.28	12.766%	$140.1456	$140.15	$140.15	$140.10
Purchase #5	$78.80	12.310%	$88.5003	$88.50	$88.50	$88.50
Purchase #6	$72.40	9.839%	$79.5234	$79.52	$79.50	$79.50
Purchase #7	$184.72	11.249%	$205.4992	$205.50	$205.50	$205.50
7 purchase totals =	$955.49		$1,055.8166	$1,055.82	$1,055.80	$1,055.80