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	$161.91	11.663%	$180.7936	$180.79	$180.80	$180.80
Purchase #2	$205.98	6.364%	$219.0886	$219.09	$219.10	$219.10
Purchase #3	$187.89	4.642%	$196.6119	$196.61	$196.60	$196.60
Purchase #4	$6.41	13.459%	$7.2727	$7.27	$7.25	$7.30
Purchase #5	$9.35	11.401%	$10.416	$10.42	$10.40	$10.40
Purchase #6	$220.88	10.162%	$243.3258	$243.33	$243.35	$243.30
Purchase #7	$23.30	7.422%	$25.0293	$25.03	$25.05	$25.00
7 purchase totals =	$815.72		$882.5379	$882.54	$882.55	$882.50