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	$223.29	9.408%	$244.2971	$244.30	$244.30	$244.30
Purchase #2	$175.76	5.137%	$184.7888	$184.79	$184.80	$184.80
Purchase #3	$72.34	10.173%	$79.6991	$79.70	$79.70	$79.70
Purchase #4	$92.60	12.460%	$104.138	$104.14	$104.15	$104.10
Purchase #5	$94.59	4.228%	$98.5893	$98.59	$98.60	$98.60
Purchase #6	$97.98	8.104%	$105.9203	$105.92	$105.90	$105.90
Purchase #7	$189.58	10.483%	$209.4537	$209.45	$209.45	$209.50
7 purchase totals =	$946.14		$1,026.8863	$1,026.89	$1,026.90	$1,026.90