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	$232.90	13.498%	$264.3368	$264.34	$264.35	$264.30
Purchase #2	$22.73	3.868%	$23.6092	$23.61	$23.60	$23.60
Purchase #3	$105.75	3.440%	$109.3878	$109.39	$109.40	$109.40
Purchase #4	$11.84	4.318%	$12.3513	$12.35	$12.35	$12.40
Purchase #5	$135.42	7.497%	$145.5724	$145.57	$145.55	$145.60
Purchase #6	$184.38	3.781%	$191.3514	$191.35	$191.35	$191.40
Purchase #7	$140.89	3.821%	$146.2734	$146.27	$146.25	$146.30
7 purchase totals =	$833.91		$892.8823	$892.88	$892.85	$893.00