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	$129.36	10.125%	$142.4577	$142.46	$142.45	$142.50
Purchase #2	$224.96	6.174%	$238.849	$238.85	$238.85	$238.80
Purchase #3	$54.61	6.162%	$57.9751	$57.98	$58.00	$58.00
Purchase #4	$134.54	12.629%	$151.5311	$151.53	$151.55	$151.50
Purchase #5	$54.77	12.418%	$61.5713	$61.57	$61.55	$61.60
Purchase #6	$48.82	9.103%	$53.2641	$53.26	$53.25	$53.30
Purchase #7	$221.72	9.222%	$242.167	$242.17	$242.15	$242.20
7 purchase totals =	$868.78		$947.8153	$947.82	$947.80	$947.90