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	$118.67	7.391%	$127.4409	$127.44	$127.45	$127.40
Purchase #2	$206.91	5.697%	$218.6977	$218.70	$218.70	$218.70
Purchase #3	$5.96	12.280%	$6.6919	$6.69	$6.70	$6.70
Purchase #4	$219.58	13.410%	$249.0257	$249.03	$249.05	$249.00
Purchase #5	$62.25	5.782%	$65.8493	$65.85	$65.85	$65.80
Purchase #6	$168.98	12.415%	$189.9589	$189.96	$189.95	$190.00
Purchase #7	$105.85	5.721%	$111.9057	$111.91	$111.90	$111.90
7 purchase totals =	$888.20		$969.5701	$969.58	$969.60	$969.50