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	$99.75	4.419%	$104.158	$104.16	$104.15	$104.20
Purchase #2	$24.68	12.741%	$27.8245	$27.82	$27.80	$27.80
Purchase #3	$209.71	11.561%	$233.9546	$233.95	$233.95	$234.00
Purchase #4	$180.66	8.543%	$196.0938	$196.09	$196.10	$196.10
Purchase #5	$130.71	10.251%	$144.1091	$144.11	$144.10	$144.10
Purchase #6	$64.67	13.417%	$73.3468	$73.35	$73.35	$73.30
Purchase #7	$246.32	10.772%	$272.8536	$272.85	$272.85	$272.90
7 purchase totals =	$956.50		$1,052.3404	$1,052.33	$1,052.30	$1,052.40