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	$222.37	8.187%	$240.5754	$240.58	$240.60	$240.60
Purchase #2	$74.70	3.728%	$77.4848	$77.48	$77.50	$77.50
Purchase #3	$145.91	6.597%	$155.5357	$155.54	$155.55	$155.50
Purchase #4	$55.31	13.581%	$62.8217	$62.82	$62.80	$62.80
Purchase #5	$133.97	6.654%	$142.8844	$142.88	$142.90	$142.90
Purchase #6	$127.76	4.665%	$133.72	$133.72	$133.70	$133.70
Purchase #7	$216.37	7.335%	$232.2407	$232.24	$232.25	$232.20
7 purchase totals =	$976.39		$1,045.2627	$1,045.26	$1,045.30	$1,045.20