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	$183.69	7.804%	$198.0252	$198.03	$198.05	$198.00
Purchase #2	$80.43	7.597%	$86.5403	$86.54	$86.55	$86.50
Purchase #3	$22.57	7.492%	$24.2609	$24.26	$24.25	$24.30
Purchase #4	$117.32	8.444%	$127.2265	$127.23	$127.25	$127.20
Purchase #5	$111.40	13.399%	$126.3265	$126.33	$126.35	$126.30
Purchase #6	$89.52	11.771%	$100.0574	$100.06	$100.05	$100.10
Purchase #7	$243.44	3.269%	$251.3981	$251.40	$251.40	$251.40
7 purchase totals =	$848.37		$913.8349	$913.85	$913.90	$913.80