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	$77.76	6.663%	$82.9411	$82.94	$82.95	$82.90
Purchase #2	$86.48	4.178%	$90.0931	$90.09	$90.10	$90.10
Purchase #3	$95.70	5.665%	$101.1214	$101.12	$101.10	$101.10
Purchase #4	$238.53	11.463%	$265.8727	$265.87	$265.85	$265.90
Purchase #5	$196.49	5.156%	$206.621	$206.62	$206.60	$206.60
Purchase #6	$165.33	9.446%	$180.9471	$180.95	$180.95	$180.90
Purchase #7	$245.67	3.630%	$254.5878	$254.59	$254.60	$254.60
7 purchase totals =	$1,105.96		$1,182.1842	$1,182.18	$1,182.15	$1,182.10