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	$142.63	5.334%	$150.2379	$150.24	$150.25	$150.20
Purchase #2	$97.39	8.309%	$105.4821	$105.48	$105.50	$105.50
Purchase #3	$134.96	12.642%	$152.0216	$152.02	$152.00	$152.00
Purchase #4	$177.63	3.616%	$184.0531	$184.05	$184.05	$184.10
Purchase #5	$204.27	5.156%	$214.8022	$214.80	$214.80	$214.80
Purchase #6	$54.66	9.667%	$59.944	$59.94	$59.95	$59.90
Purchase #7	$162.51	11.153%	$180.6347	$180.63	$180.65	$180.60
7 purchase totals =	$974.05		$1,047.1756	$1,047.16	$1,047.20	$1,047.10