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	$207.30	6.533%	$220.8429	$220.84	$220.85	$220.80
Purchase #2	$28.71	10.787%	$31.8069	$31.81	$31.80	$31.80
Purchase #3	$228.48	6.576%	$243.5048	$243.50	$243.50	$243.50
Purchase #4	$173.58	8.440%	$188.2302	$188.23	$188.25	$188.20
Purchase #5	$30.85	9.768%	$33.8634	$33.86	$33.85	$33.90
Purchase #6	$200.72	7.184%	$215.1397	$215.14	$215.15	$215.10
Purchase #7	$72.79	9.251%	$79.5238	$79.52	$79.50	$79.50
7 purchase totals =	$942.43		$1,012.9117	$1,012.90	$1,012.90	$1,012.80