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	$234.62	13.702%	$266.7676	$266.77	$266.75	$266.80
Purchase #2	$36.97	5.121%	$38.8632	$38.86	$38.85	$38.90
Purchase #3	$187.92	7.301%	$201.64	$201.64	$201.65	$201.60
Purchase #4	$210.30	13.324%	$238.3204	$238.32	$238.30	$238.30
Purchase #5	$100.85	12.454%	$113.4099	$113.41	$113.40	$113.40
Purchase #6	$73.56	6.731%	$78.5113	$78.51	$78.50	$78.50
Purchase #7	$190.98	9.864%	$209.8183	$209.82	$209.80	$209.80
7 purchase totals =	$1,035.20		$1,147.3307	$1,147.33	$1,147.25	$1,147.30