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	$71.85	12.298%	$80.6861	$80.69	$80.70	$80.70
Purchase #2	$195.51	7.641%	$210.4489	$210.45	$210.45	$210.40
Purchase #3	$244.89	11.646%	$273.4099	$273.41	$273.40	$273.40
Purchase #4	$36.98	12.648%	$41.6572	$41.66	$41.65	$41.70
Purchase #5	$59.66	12.283%	$66.988	$66.99	$67.00	$67.00
Purchase #6	$166.32	3.189%	$171.6239	$171.62	$171.60	$171.60
Purchase #7	$229.35	9.272%	$250.6153	$250.62	$250.60	$250.60
7 purchase totals =	$1,004.56		$1,095.4293	$1,095.44	$1,095.40	$1,095.40