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	$184.65	8.724%	$200.7589	$200.76	$200.75	$200.80
Purchase #2	$213.51	10.410%	$235.7364	$235.74	$235.75	$235.70
Purchase #3	$142.58	5.493%	$150.4119	$150.41	$150.40	$150.40
Purchase #4	$200.66	4.304%	$209.2964	$209.30	$209.30	$209.30
Purchase #5	$48.92	11.220%	$54.4088	$54.41	$54.40	$54.40
Purchase #6	$187.40	8.835%	$203.9568	$203.96	$203.95	$204.00
Purchase #7	$117.30	8.712%	$127.5192	$127.52	$127.50	$127.50
7 purchase totals =	$1,095.02		$1,182.0884	$1,182.10	$1,182.05	$1,182.10