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	$146.51	13.218%	$165.8757	$165.88	$165.90	$165.90
Purchase #2	$147.91	4.272%	$154.2287	$154.23	$154.25	$154.20
Purchase #3	$162.78	13.836%	$185.3022	$185.30	$185.30	$185.30
Purchase #4	$86.57	6.280%	$92.0066	$92.01	$92.00	$92.00
Purchase #5	$132.65	10.724%	$146.8754	$146.88	$146.90	$146.90
Purchase #6	$116.70	13.380%	$132.3145	$132.31	$132.30	$132.30
Purchase #7	$126.92	13.717%	$144.3296	$144.33	$144.35	$144.30
7 purchase totals =	$920.04		$1,020.9327	$1,020.94	$1,021.00	$1,020.90