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	$139.89	11.321%	$155.7269	$155.73	$155.75	$155.70
Purchase #2	$130.41	13.305%	$147.7611	$147.76	$147.75	$147.80
Purchase #3	$239.40	6.725%	$255.4997	$255.50	$255.50	$255.50
Purchase #4	$23.25	3.720%	$24.1149	$24.11	$24.10	$24.10
Purchase #5	$154.73	13.450%	$175.5412	$175.54	$175.55	$175.50
Purchase #6	$92.48	4.218%	$96.3808	$96.38	$96.40	$96.40
Purchase #7	$187.57	4.781%	$196.5377	$196.54	$196.55	$196.50
7 purchase totals =	$967.73		$1,051.5623	$1,051.56	$1,051.60	$1,051.50