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	$151.82	11.541%	$169.3415	$169.34	$169.35	$169.30
Purchase #2	$48.81	11.418%	$54.3831	$54.38	$54.40	$54.40
Purchase #3	$118.92	12.556%	$133.8516	$133.85	$133.85	$133.90
Purchase #4	$78.39	5.688%	$82.8488	$82.85	$82.85	$82.80
Purchase #5	$233.76	11.846%	$261.4512	$261.45	$261.45	$261.50
Purchase #6	$54.33	6.255%	$57.7283	$57.73	$57.75	$57.70
Purchase #7	$42.39	5.597%	$44.7626	$44.76	$44.75	$44.80
7 purchase totals =	$728.42		$804.3671	$804.36	$804.40	$804.40