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	$97.61	10.626%	$107.982	$107.98	$108.00	$108.00
Purchase #2	$174.74	6.205%	$185.5826	$185.58	$185.60	$185.60
Purchase #3	$215.50	9.559%	$236.0996	$236.10	$236.10	$236.10
Purchase #4	$77.66	4.139%	$80.8743	$80.87	$80.85	$80.90
Purchase #5	$99.94	11.616%	$111.549	$111.55	$111.55	$111.50
Purchase #6	$200.62	11.741%	$224.1748	$224.17	$224.15	$224.20
Purchase #7	$185.26	5.555%	$195.5512	$195.55	$195.55	$195.60
7 purchase totals =	$1,051.33		$1,141.8135	$1,141.80	$1,141.80	$1,141.90