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	$136.70	6.274%	$145.2766	$145.28	$145.30	$145.30
Purchase #2	$220.32	9.171%	$240.5255	$240.53	$240.55	$240.50
Purchase #3	$104.59	8.526%	$113.5073	$113.51	$113.50	$113.50
Purchase #4	$209.36	11.513%	$233.4636	$233.46	$233.45	$233.50
Purchase #5	$56.66	4.569%	$59.2488	$59.25	$59.25	$59.20
Purchase #6	$50.57	9.749%	$55.5001	$55.50	$55.50	$55.50
Purchase #7	$148.51	13.550%	$168.6331	$168.63	$168.65	$168.60
7 purchase totals =	$926.71		$1,016.1550	$1,016.16	$1,016.20	$1,016.10