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	$175.90	7.761%	$189.5516	$189.55	$189.55	$189.60
Purchase #2	$177.69	5.818%	$188.028	$188.03	$188.05	$188.00
Purchase #3	$43.93	12.769%	$49.5394	$49.54	$49.55	$49.50
Purchase #4	$105.42	11.373%	$117.4094	$117.41	$117.40	$117.40
Purchase #5	$183.27	3.363%	$189.4334	$189.43	$189.45	$189.40
Purchase #6	$85.27	7.292%	$91.4879	$91.49	$91.50	$91.50
Purchase #7	$92.59	8.276%	$100.2527	$100.25	$100.25	$100.30
7 purchase totals =	$864.07		$925.7024	$925.70	$925.75	$925.70