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	$177.95	5.636%	$187.9793	$187.98	$188.00	$188.00
Purchase #2	$42.54	4.659%	$44.5219	$44.52	$44.50	$44.50
Purchase #3	$240.97	5.238%	$253.592	$253.59	$253.60	$253.60
Purchase #4	$65.69	11.592%	$73.3048	$73.30	$73.30	$73.30
Purchase #5	$153.36	7.188%	$164.3835	$164.38	$164.40	$164.40
Purchase #6	$28.44	7.179%	$30.4817	$30.48	$30.50	$30.50
Purchase #7	$244.66	4.449%	$255.5449	$255.54	$255.55	$255.50
7 purchase totals =	$953.61		$1,009.8081	$1,009.79	$1,009.85	$1,009.80