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	$202.58	10.722%	$224.3006	$224.30	$224.30	$224.30
Purchase #2	$191.61	11.428%	$213.5072	$213.51	$213.50	$213.50
Purchase #3	$51.41	8.190%	$55.6205	$55.62	$55.60	$55.60
Purchase #4	$91.99	8.869%	$100.1486	$100.15	$100.15	$100.10
Purchase #5	$63.49	12.425%	$71.3786	$71.38	$71.40	$71.40
Purchase #6	$100.93	8.625%	$109.6352	$109.64	$109.65	$109.60
Purchase #7	$35.97	11.465%	$40.094	$40.09	$40.10	$40.10
7 purchase totals =	$737.98		$814.6847	$814.69	$814.70	$814.60