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	$155.31	13.156%	$175.7426	$175.74	$175.75	$175.70
Purchase #2	$20.76	8.369%	$22.4974	$22.50	$22.50	$22.50
Purchase #3	$97.92	9.705%	$107.4231	$107.42	$107.40	$107.40
Purchase #4	$112.80	11.265%	$125.5069	$125.51	$125.50	$125.50
Purchase #5	$159.46	11.705%	$178.1248	$178.12	$178.10	$178.10
Purchase #6	$127.31	3.541%	$131.818	$131.82	$131.80	$131.80
Purchase #7	$95.73	13.349%	$108.509	$108.51	$108.50	$108.50
7 purchase totals =	$769.29		$849.6218	$849.62	$849.55	$849.50