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	$228.80	6.106%	$242.7705	$242.77	$242.75	$242.80
Purchase #2	$89.65	11.456%	$99.9203	$99.92	$99.90	$99.90
Purchase #3	$95.85	8.301%	$103.8065	$103.81	$103.80	$103.80
Purchase #4	$249.52	7.712%	$268.763	$268.76	$268.75	$268.80
Purchase #5	$194.52	13.569%	$220.9144	$220.91	$220.90	$220.90
Purchase #6	$55.60	12.774%	$62.7023	$62.70	$62.70	$62.70
Purchase #7	$48.81	9.762%	$53.5748	$53.57	$53.55	$53.60
7 purchase totals =	$962.75		$1,052.4518	$1,052.44	$1,052.35	$1,052.50