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	$119.37	11.733%	$133.3757	$133.38	$133.40	$133.40
Purchase #2	$250.79	9.784%	$275.3273	$275.33	$275.35	$275.30
Purchase #3	$46.91	7.238%	$50.3053	$50.31	$50.30	$50.30
Purchase #4	$168.45	12.238%	$189.0649	$189.06	$189.05	$189.10
Purchase #5	$80.34	4.226%	$83.7352	$83.74	$83.75	$83.70
Purchase #6	$204.52	3.673%	$212.032	$212.03	$212.05	$212.00
Purchase #7	$133.99	6.103%	$142.1674	$142.17	$142.15	$142.20
7 purchase totals =	$1,004.37		$1,086.0078	$1,086.02	$1,086.05	$1,086.00