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	$232.39	5.164%	$244.3906	$244.39	$244.40	$244.40
Purchase #2	$210.90	3.376%	$218.02	$218.02	$218.00	$218.00
Purchase #3	$73.76	11.829%	$82.4851	$82.49	$82.50	$82.50
Purchase #4	$152.62	10.241%	$168.2498	$168.25	$168.25	$168.20
Purchase #5	$227.31	6.747%	$242.6466	$242.65	$242.65	$242.60
Purchase #6	$226.82	4.717%	$237.5191	$237.52	$237.50	$237.50
Purchase #7	$123.91	12.853%	$139.8362	$139.84	$139.85	$139.80
7 purchase totals =	$1,247.71		$1,333.1474	$1,333.16	$1,333.15	$1,333.00