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	$206.64	10.340%	$228.0066	$228.01	$228.00	$228.00
Purchase #2	$39.33	10.763%	$43.5631	$43.56	$43.55	$43.60
Purchase #3	$167.41	13.636%	$190.238	$190.24	$190.25	$190.20
Purchase #4	$189.41	10.824%	$209.9117	$209.91	$209.90	$209.90
Purchase #5	$173.74	7.305%	$186.4317	$186.43	$186.45	$186.40
Purchase #6	$60.34	3.460%	$62.4278	$62.43	$62.45	$62.40
Purchase #7	$69.39	13.532%	$78.7799	$78.78	$78.80	$78.80
7 purchase totals =	$906.26		$999.3588	$999.36	$999.40	$999.30