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	$185.25	4.852%	$194.2383	$194.24	$194.25	$194.20
Purchase #2	$103.68	6.530%	$110.4503	$110.45	$110.45	$110.50
Purchase #3	$156.45	6.300%	$166.3064	$166.31	$166.30	$166.30
Purchase #4	$131.87	8.693%	$143.3335	$143.33	$143.35	$143.30
Purchase #5	$105.64	13.185%	$119.5686	$119.57	$119.55	$119.60
Purchase #6	$196.50	6.803%	$209.8679	$209.87	$209.85	$209.90
Purchase #7	$182.27	12.719%	$205.4529	$205.45	$205.45	$205.50
7 purchase totals =	$1,061.66		$1,149.2179	$1,149.22	$1,149.20	$1,149.30