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	$140.92	7.250%	$151.1367	$151.14	$151.15	$151.10
Purchase #2	$96.89	12.256%	$108.7648	$108.76	$108.75	$108.80
Purchase #3	$185.33	10.783%	$205.3141	$205.31	$205.30	$205.30
Purchase #4	$109.34	4.376%	$114.1247	$114.12	$114.10	$114.10
Purchase #5	$29.73	10.202%	$32.7631	$32.76	$32.75	$32.80
Purchase #6	$139.93	11.746%	$156.3662	$156.37	$156.35	$156.40
Purchase #7	$178.61	6.473%	$190.1714	$190.17	$190.15	$190.20
7 purchase totals =	$880.75		$958.6410	$958.63	$958.55	$958.70