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	$176.53	8.614%	$191.7363	$191.74	$191.75	$191.70
Purchase #2	$161.39	3.106%	$166.4028	$166.40	$166.40	$166.40
Purchase #3	$159.50	4.377%	$166.4813	$166.48	$166.50	$166.50
Purchase #4	$83.93	6.205%	$89.1379	$89.14	$89.15	$89.10
Purchase #5	$130.28	9.337%	$142.4442	$142.44	$142.45	$142.40
Purchase #6	$100.30	9.403%	$109.7312	$109.73	$109.75	$109.70
Purchase #7	$14.60	3.761%	$15.1491	$15.15	$15.15	$15.10
7 purchase totals =	$826.53		$881.0828	$881.08	$881.15	$880.90