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	$215.96	13.825%	$245.8165	$245.82	$245.80	$245.80
Purchase #2	$227.59	7.245%	$244.0789	$244.08	$244.10	$244.10
Purchase #3	$212.26	8.127%	$229.5104	$229.51	$229.50	$229.50
Purchase #4	$112.26	10.300%	$123.8228	$123.82	$123.80	$123.80
Purchase #5	$124.94	4.413%	$130.4536	$130.45	$130.45	$130.50
Purchase #6	$150.25	10.816%	$166.501	$166.50	$166.50	$166.50
Purchase #7	$32.25	5.329%	$33.9686	$33.97	$33.95	$34.00
7 purchase totals =	$1,075.51		$1,174.1518	$1,174.15	$1,174.10	$1,174.20