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	$239.40	9.320%	$261.7121	$261.71	$261.70	$261.70
Purchase #2	$27.92	4.110%	$29.0675	$29.07	$29.05	$29.10
Purchase #3	$175.40	9.170%	$191.4842	$191.48	$191.50	$191.50
Purchase #4	$137.75	13.181%	$155.9068	$155.91	$155.90	$155.90
Purchase #5	$245.66	10.271%	$270.8917	$270.89	$270.90	$270.90
Purchase #6	$103.74	3.435%	$107.3035	$107.30	$107.30	$107.30
Purchase #7	$41.25	9.548%	$45.1886	$45.19	$45.20	$45.20
7 purchase totals =	$971.12		$1,061.5544	$1,061.55	$1,061.55	$1,061.60