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	$98.77	6.833%	$105.519	$105.52	$105.50	$105.50
Purchase #2	$16.55	8.173%	$17.9026	$17.90	$17.90	$17.90
Purchase #3	$88.35	3.655%	$91.5792	$91.58	$91.60	$91.60
Purchase #4	$245.84	4.135%	$256.0055	$256.01	$256.00	$256.00
Purchase #5	$72.54	5.260%	$76.3556	$76.36	$76.35	$76.40
Purchase #6	$90.39	10.741%	$100.0988	$100.10	$100.10	$100.10
Purchase #7	$213.28	7.400%	$229.0627	$229.06	$229.05	$229.10
7 purchase totals =	$825.72		$876.5234	$876.53	$876.50	$876.60