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	$204.67	8.870%	$222.8242	$222.82	$222.80	$222.80
Purchase #2	$19.93	4.183%	$20.7637	$20.76	$20.75	$20.80
Purchase #3	$75.92	12.492%	$85.4039	$85.40	$85.40	$85.40
Purchase #4	$53.91	3.159%	$55.613	$55.61	$55.60	$55.60
Purchase #5	$48.53	9.104%	$52.9482	$52.95	$52.95	$52.90
Purchase #6	$128.70	3.354%	$133.0166	$133.02	$133.00	$133.00
Purchase #7	$245.41	3.274%	$253.4447	$253.44	$253.45	$253.40
7 purchase totals =	$777.07		$824.0143	$824.00	$823.95	$823.90