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	$57.63	3.671%	$59.7456	$59.75	$59.75	$59.70
Purchase #2	$82.77	13.254%	$93.7403	$93.74	$93.75	$93.70
Purchase #3	$83.51	8.677%	$90.7562	$90.76	$90.75	$90.80
Purchase #4	$146.71	10.665%	$162.3566	$162.36	$162.35	$162.40
Purchase #5	$248.87	6.443%	$264.9047	$264.90	$264.90	$264.90
Purchase #6	$240.92	10.327%	$265.7998	$265.80	$265.80	$265.80
Purchase #7	$180.37	13.489%	$204.7001	$204.70	$204.70	$204.70
7 purchase totals =	$1,040.78		$1,142.0033	$1,142.01	$1,142.00	$1,142.00