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	$169.56	8.416%	$183.8302	$183.83	$183.85	$183.80
Purchase #2	$103.27	8.305%	$111.8466	$111.85	$111.85	$111.80
Purchase #3	$128.32	10.667%	$142.0079	$142.01	$142.00	$142.00
Purchase #4	$250.49	7.310%	$268.8008	$268.80	$268.80	$268.80
Purchase #5	$80.41	12.822%	$90.7202	$90.72	$90.70	$90.70
Purchase #6	$244.62	9.806%	$268.6074	$268.61	$268.60	$268.60
Purchase #7	$102.77	4.132%	$107.0165	$107.02	$107.00	$107.00
7 purchase totals =	$1,079.44		$1,172.8296	$1,172.84	$1,172.80	$1,172.70