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	$156.52	10.356%	$172.7292	$172.73	$172.75	$172.70
Purchase #2	$148.49	5.355%	$156.4416	$156.44	$156.45	$156.40
Purchase #3	$104.72	6.664%	$111.6985	$111.70	$111.70	$111.70
Purchase #4	$219.91	3.785%	$228.2336	$228.23	$228.25	$228.20
Purchase #5	$137.49	9.186%	$150.1198	$150.12	$150.10	$150.10
Purchase #6	$93.40	7.529%	$100.4321	$100.43	$100.45	$100.40
Purchase #7	$76.54	6.338%	$81.3911	$81.39	$81.40	$81.40
7 purchase totals =	$937.07		$1,001.0459	$1,001.04	$1,001.10	$1,000.90