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	$33.92	10.640%	$37.5291	$37.53	$37.55	$37.50
Purchase #2	$157.31	3.230%	$162.3911	$162.39	$162.40	$162.40
Purchase #3	$113.43	12.320%	$127.4046	$127.40	$127.40	$127.40
Purchase #4	$208.61	4.394%	$217.7763	$217.78	$217.80	$217.80
Purchase #5	$242.94	11.612%	$271.1502	$271.15	$271.15	$271.20
Purchase #6	$185.56	11.775%	$207.4097	$207.41	$207.40	$207.40
Purchase #7	$152.56	4.396%	$159.2665	$159.27	$159.25	$159.30
7 purchase totals =	$1,094.33		$1,182.9275	$1,182.93	$1,182.95	$1,183.00