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	$163.73	4.814%	$171.612	$171.61	$171.60	$171.60
Purchase #2	$195.52	11.618%	$218.2355	$218.24	$218.25	$218.20
Purchase #3	$73.62	11.635%	$82.1857	$82.19	$82.20	$82.20
Purchase #4	$118.70	13.363%	$134.5619	$134.56	$134.55	$134.60
Purchase #5	$178.87	12.321%	$200.9086	$200.91	$200.90	$200.90
Purchase #6	$132.53	10.732%	$146.7531	$146.75	$146.75	$146.80
Purchase #7	$125.59	13.666%	$142.7531	$142.75	$142.75	$142.80
7 purchase totals =	$988.56		$1,097.0099	$1,097.01	$1,097.00	$1,097.10