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	$219.94	4.198%	$229.1731	$229.17	$229.15	$229.20
Purchase #2	$16.41	11.380%	$18.2775	$18.28	$18.30	$18.30
Purchase #3	$21.34	9.741%	$23.4187	$23.42	$23.40	$23.40
Purchase #4	$129.46	11.815%	$144.7557	$144.76	$144.75	$144.80
Purchase #5	$47.92	11.624%	$53.4902	$53.49	$53.50	$53.50
Purchase #6	$53.57	4.682%	$56.0781	$56.08	$56.10	$56.10
Purchase #7	$127.26	13.650%	$144.631	$144.63	$144.65	$144.60
7 purchase totals =	$615.90		$669.8243	$669.83	$669.85	$669.90