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	$234.90	5.279%	$247.3004	$247.30	$247.30	$247.30
Purchase #2	$95.41	4.391%	$99.5995	$99.60	$99.60	$99.60
Purchase #3	$246.79	6.186%	$262.0564	$262.06	$262.05	$262.10
Purchase #4	$225.89	11.721%	$252.3666	$252.37	$252.35	$252.40
Purchase #5	$162.39	6.413%	$172.8041	$172.80	$172.80	$172.80
Purchase #6	$48.78	7.275%	$52.3287	$52.33	$52.35	$52.30
Purchase #7	$85.67	5.233%	$90.1531	$90.15	$90.15	$90.20
7 purchase totals =	$1,099.83		$1,176.6088	$1,176.61	$1,176.60	$1,176.70