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	$217.74	4.857%	$228.3156	$228.32	$228.30	$228.30
Purchase #2	$79.85	3.859%	$82.9314	$82.93	$82.95	$82.90
Purchase #3	$124.48	4.309%	$129.8438	$129.84	$129.85	$129.80
Purchase #4	$18.36	11.578%	$20.4857	$20.49	$20.50	$20.50
Purchase #5	$144.69	7.409%	$155.4101	$155.41	$155.40	$155.40
Purchase #6	$240.40	6.856%	$256.8818	$256.88	$256.90	$256.90
Purchase #7	$206.95	4.728%	$216.7346	$216.73	$216.75	$216.70
7 purchase totals =	$1,032.47		$1,090.6030	$1,090.60	$1,090.65	$1,090.50