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	$119.39	4.279%	$124.4987	$124.50	$124.50	$124.50
Purchase #2	$73.77	13.264%	$83.5549	$83.55	$83.55	$83.60
Purchase #3	$67.64	7.506%	$72.7171	$72.72	$72.70	$72.70
Purchase #4	$223.66	10.858%	$247.945	$247.95	$247.95	$247.90
Purchase #5	$245.60	4.595%	$256.8853	$256.89	$256.90	$256.90
Purchase #6	$215.32	13.234%	$243.8154	$243.82	$243.80	$243.80
Purchase #7	$33.42	5.425%	$35.233	$35.23	$35.25	$35.20
7 purchase totals =	$978.80		$1,064.6494	$1,064.66	$1,064.65	$1,064.60