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	$183.46	8.346%	$198.7716	$198.77	$198.75	$198.80
Purchase #2	$176.31	6.311%	$187.4369	$187.44	$187.45	$187.40
Purchase #3	$63.37	6.380%	$67.413	$67.41	$67.40	$67.40
Purchase #4	$246.85	11.320%	$274.7934	$274.79	$274.80	$274.80
Purchase #5	$106.71	11.354%	$118.8259	$118.83	$118.85	$118.80
Purchase #6	$90.69	9.188%	$99.0226	$99.02	$99.00	$99.00
Purchase #7	$73.96	12.286%	$83.0467	$83.05	$83.05	$83.00
7 purchase totals =	$941.35		$1,029.3101	$1,029.31	$1,029.30	$1,029.20