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	$226.51	5.567%	$239.1198	$239.12	$239.10	$239.10
Purchase #2	$181.98	7.842%	$196.2509	$196.25	$196.25	$196.30
Purchase #3	$44.75	7.277%	$48.0065	$48.01	$48.00	$48.00
Purchase #4	$28.86	12.471%	$32.4591	$32.46	$32.45	$32.50
Purchase #5	$250.72	7.565%	$269.687	$269.69	$269.70	$269.70
Purchase #6	$34.73	3.504%	$35.9469	$35.95	$35.95	$35.90
Purchase #7	$174.59	6.114%	$185.2644	$185.26	$185.25	$185.30
7 purchase totals =	$942.14		$1,006.7346	$1,006.74	$1,006.70	$1,006.80