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	$98.82	6.708%	$105.4488	$105.45	$105.45	$105.40
Purchase #2	$125.84	12.188%	$141.1774	$141.18	$141.20	$141.20
Purchase #3	$59.97	6.653%	$63.9598	$63.96	$63.95	$64.00
Purchase #4	$138.67	9.778%	$152.2292	$152.23	$152.25	$152.20
Purchase #5	$232.96	13.786%	$265.0759	$265.08	$265.10	$265.10
Purchase #6	$167.52	10.812%	$185.6323	$185.63	$185.65	$185.60
Purchase #7	$207.88	10.219%	$229.1233	$229.12	$229.10	$229.10
7 purchase totals =	$1,031.66		$1,142.6467	$1,142.65	$1,142.70	$1,142.60