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	$78.30	10.132%	$86.2334	$86.23	$86.25	$86.20
Purchase #2	$55.98	5.364%	$58.9828	$58.98	$59.00	$59.00
Purchase #3	$73.59	13.786%	$83.7351	$83.74	$83.75	$83.70
Purchase #4	$240.85	11.621%	$268.8392	$268.84	$268.85	$268.80
Purchase #5	$137.92	7.648%	$148.4681	$148.47	$148.45	$148.50
Purchase #6	$136.28	10.647%	$150.7897	$150.79	$150.80	$150.80
Purchase #7	$163.27	12.796%	$184.162	$184.16	$184.15	$184.20
7 purchase totals =	$886.19		$981.2103	$981.21	$981.25	$981.20