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	$146.74	6.612%	$156.4424	$156.44	$156.45	$156.40
Purchase #2	$81.29	12.691%	$91.6065	$91.61	$91.60	$91.60
Purchase #3	$240.52	11.867%	$269.0625	$269.06	$269.05	$269.10
Purchase #4	$112.29	9.740%	$123.227	$123.23	$123.25	$123.20
Purchase #5	$206.98	3.168%	$213.5371	$213.54	$213.55	$213.50
Purchase #6	$127.44	7.150%	$136.552	$136.55	$136.55	$136.60
Purchase #7	$139.76	4.615%	$146.2099	$146.21	$146.20	$146.20
7 purchase totals =	$1,055.02		$1,136.6374	$1,136.64	$1,136.65	$1,136.60