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	$130.69	4.701%	$136.8337	$136.83	$136.85	$136.80
Purchase #2	$58.57	10.227%	$64.56	$64.56	$64.55	$64.60
Purchase #3	$166.56	13.194%	$188.5359	$188.54	$188.55	$188.50
Purchase #4	$190.69	6.365%	$202.8274	$202.83	$202.85	$202.80
Purchase #5	$142.98	11.476%	$159.3884	$159.39	$159.40	$159.40
Purchase #6	$127.54	10.105%	$140.4279	$140.43	$140.45	$140.40
Purchase #7	$162.69	12.259%	$182.6342	$182.63	$182.65	$182.60
7 purchase totals =	$979.72		$1,075.2075	$1,075.21	$1,075.30	$1,075.10