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	$241.43	10.337%	$266.3866	$266.39	$266.40	$266.40
Purchase #2	$95.26	12.227%	$106.9074	$106.91	$106.90	$106.90
Purchase #3	$122.45	7.649%	$131.8162	$131.82	$131.80	$131.80
Purchase #4	$19.68	3.161%	$20.3021	$20.30	$20.30	$20.30
Purchase #5	$127.31	5.374%	$134.1516	$134.15	$134.15	$134.20
Purchase #6	$181.51	5.289%	$191.1101	$191.11	$191.10	$191.10
Purchase #7	$156.35	8.193%	$169.1598	$169.16	$169.15	$169.20
7 purchase totals =	$943.99		$1,019.8338	$1,019.84	$1,019.80	$1,019.90