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	$69.55	6.751%	$74.2453	$74.25	$74.25	$74.20
Purchase #2	$54.64	5.314%	$57.5436	$57.54	$57.55	$57.50
Purchase #3	$67.38	6.137%	$71.5151	$71.52	$71.50	$71.50
Purchase #4	$177.85	4.669%	$186.1538	$186.15	$186.15	$186.20
Purchase #5	$56.41	11.464%	$62.8768	$62.88	$62.90	$62.90
Purchase #6	$179.72	9.215%	$196.2812	$196.28	$196.30	$196.30
Purchase #7	$242.60	12.434%	$272.7649	$272.76	$272.75	$272.80
7 purchase totals =	$848.15		$921.3807	$921.38	$921.40	$921.40