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	$64.64	8.464%	$70.1111	$70.11	$70.10	$70.10
Purchase #2	$190.45	9.471%	$208.4875	$208.49	$208.50	$208.50
Purchase #3	$153.30	10.120%	$168.814	$168.81	$168.80	$168.80
Purchase #4	$95.82	3.868%	$99.5263	$99.53	$99.55	$99.50
Purchase #5	$212.84	3.658%	$220.6257	$220.63	$220.65	$220.60
Purchase #6	$104.32	5.233%	$109.7791	$109.78	$109.80	$109.80
Purchase #7	$153.98	11.552%	$171.7678	$171.77	$171.75	$171.80
7 purchase totals =	$975.35		$1,049.1115	$1,049.12	$1,049.15	$1,049.10