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	$181.76	5.310%	$191.4115	$191.41	$191.40	$191.40
Purchase #2	$18.86	12.715%	$21.258	$21.26	$21.25	$21.30
Purchase #3	$82.34	11.465%	$91.7803	$91.78	$91.80	$91.80
Purchase #4	$85.34	4.580%	$89.2486	$89.25	$89.25	$89.20
Purchase #5	$98.31	6.775%	$104.9705	$104.97	$104.95	$105.00
Purchase #6	$108.36	12.523%	$121.9299	$121.93	$121.95	$121.90
Purchase #7	$248.79	5.674%	$262.9063	$262.91	$262.90	$262.90
7 purchase totals =	$823.76		$883.5051	$883.51	$883.50	$883.50