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	$53.85	4.318%	$56.1752	$56.18	$56.20	$56.20
Purchase #2	$229.41	11.801%	$256.4827	$256.48	$256.50	$256.50
Purchase #3	$200.74	13.743%	$228.3277	$228.33	$228.35	$228.30
Purchase #4	$57.96	10.159%	$63.8482	$63.85	$63.85	$63.80
Purchase #5	$147.52	8.827%	$160.5416	$160.54	$160.55	$160.50
Purchase #6	$190.77	3.116%	$196.7144	$196.71	$196.70	$196.70
Purchase #7	$185.85	11.553%	$207.3213	$207.32	$207.30	$207.30
7 purchase totals =	$1,066.10		$1,169.4111	$1,169.41	$1,169.45	$1,169.30