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	$203.33	10.390%	$224.456	$224.46	$224.45	$224.50
Purchase #2	$44.32	4.601%	$46.3592	$46.36	$46.35	$46.40
Purchase #3	$96.46	7.253%	$103.4562	$103.46	$103.45	$103.50
Purchase #4	$32.52	7.726%	$35.0325	$35.03	$35.05	$35.00
Purchase #5	$19.93	7.446%	$21.414	$21.41	$21.40	$21.40
Purchase #6	$151.90	6.654%	$162.0074	$162.01	$162.00	$162.00
Purchase #7	$237.65	11.527%	$265.0439	$265.04	$265.05	$265.00
7 purchase totals =	$786.11		$857.7692	$857.77	$857.75	$857.80