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	$185.88	6.717%	$198.3656	$198.37	$198.35	$198.40
Purchase #2	$17.98	11.441%	$20.0371	$20.04	$20.05	$20.00
Purchase #3	$174.73	6.267%	$185.6803	$185.68	$185.70	$185.70
Purchase #4	$81.45	11.212%	$90.5822	$90.58	$90.60	$90.60
Purchase #5	$78.48	6.574%	$83.6393	$83.64	$83.65	$83.60
Purchase #6	$191.60	3.802%	$198.8846	$198.88	$198.90	$198.90
Purchase #7	$234.48	4.524%	$245.0879	$245.09	$245.10	$245.10
7 purchase totals =	$964.60		$1,022.2770	$1,022.28	$1,022.35	$1,022.30