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	$99.61	5.275%	$104.8644	$104.86	$104.85	$104.90
Purchase #2	$170.56	5.302%	$179.6031	$179.60	$179.60	$179.60
Purchase #3	$111.94	12.401%	$125.8217	$125.82	$125.80	$125.80
Purchase #4	$97.56	9.220%	$106.555	$106.56	$106.55	$106.60
Purchase #5	$235.36	6.230%	$250.0229	$250.02	$250.00	$250.00
Purchase #6	$221.27	4.119%	$230.3841	$230.38	$230.40	$230.40
Purchase #7	$76.33	8.508%	$82.8242	$82.82	$82.80	$82.80
7 purchase totals =	$1,012.63		$1,080.0754	$1,080.06	$1,080.00	$1,080.10