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	$95.58	3.771%	$99.1843	$99.18	$99.20	$99.20
Purchase #2	$177.89	3.570%	$184.2407	$184.24	$184.25	$184.20
Purchase #3	$55.59	5.275%	$58.5224	$58.52	$58.50	$58.50
Purchase #4	$62.95	7.199%	$67.4818	$67.48	$67.50	$67.50
Purchase #5	$222.93	12.782%	$251.4249	$251.42	$251.40	$251.40
Purchase #6	$208.58	4.382%	$217.72	$217.72	$217.70	$217.70
Purchase #7	$176.41	11.460%	$196.6266	$196.63	$196.65	$196.60
7 purchase totals =	$999.93		$1,075.2007	$1,075.19	$1,075.20	$1,075.10