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	$78.59	7.468%	$84.4591	$84.46	$84.45	$84.50
Purchase #2	$173.80	6.720%	$185.4794	$185.48	$185.50	$185.50
Purchase #3	$230.94	8.106%	$249.66	$249.66	$249.65	$249.70
Purchase #4	$162.75	3.227%	$168.0019	$168.00	$168.00	$168.00
Purchase #5	$85.36	5.156%	$89.7612	$89.76	$89.75	$89.80
Purchase #6	$89.63	11.506%	$99.9428	$99.94	$99.95	$99.90
Purchase #7	$188.76	4.707%	$197.6449	$197.64	$197.65	$197.60
7 purchase totals =	$1,009.83		$1,074.9493	$1,074.94	$1,074.95	$1,075.00