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	$181.29	5.383%	$191.0488	$191.05	$191.05	$191.00
Purchase #2	$57.89	12.699%	$65.2415	$65.24	$65.25	$65.20
Purchase #3	$178.51	3.444%	$184.6579	$184.66	$184.65	$184.70
Purchase #4	$248.36	10.256%	$273.8318	$273.83	$273.85	$273.80
Purchase #5	$59.49	3.438%	$61.5353	$61.54	$61.55	$61.50
Purchase #6	$208.59	9.851%	$229.1382	$229.14	$229.15	$229.10
Purchase #7	$36.82	3.559%	$38.1304	$38.13	$38.15	$38.10
7 purchase totals =	$970.95		$1,043.5839	$1,043.59	$1,043.65	$1,043.40