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	$148.73	6.192%	$157.9394	$157.94	$157.95	$157.90
Purchase #2	$64.53	11.481%	$71.9387	$71.94	$71.95	$71.90
Purchase #3	$108.69	4.207%	$113.2626	$113.26	$113.25	$113.30
Purchase #4	$117.88	4.387%	$123.0514	$123.05	$123.05	$123.10
Purchase #5	$83.55	7.459%	$89.782	$89.78	$89.80	$89.80
Purchase #6	$74.79	10.220%	$82.4335	$82.43	$82.45	$82.40
Purchase #7	$115.29	4.654%	$120.6556	$120.66	$120.65	$120.70
7 purchase totals =	$713.46		$759.0632	$759.06	$759.10	$759.10