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	$114.40	11.872%	$127.9816	$127.98	$128.00	$128.00
Purchase #2	$15.44	5.655%	$16.3131	$16.31	$16.30	$16.30
Purchase #3	$215.61	12.456%	$242.4664	$242.47	$242.45	$242.50
Purchase #4	$69.48	13.532%	$78.882	$78.88	$78.90	$78.90
Purchase #5	$210.40	5.408%	$221.7784	$221.78	$221.80	$221.80
Purchase #6	$87.79	6.370%	$93.3822	$93.38	$93.40	$93.40
Purchase #7	$204.33	11.839%	$228.5206	$228.52	$228.50	$228.50
7 purchase totals =	$917.45		$1,009.3243	$1,009.32	$1,009.35	$1,009.40