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	$103.62	6.109%	$109.9501	$109.95	$109.95	$110.00
Purchase #2	$144.59	10.152%	$159.2688	$159.27	$159.25	$159.30
Purchase #3	$68.54	7.843%	$73.9156	$73.92	$73.90	$73.90
Purchase #4	$102.26	13.743%	$116.3136	$116.31	$116.30	$116.30
Purchase #5	$200.31	8.132%	$216.5992	$216.60	$216.60	$216.60
Purchase #6	$116.85	5.570%	$123.3585	$123.36	$123.35	$123.40
Purchase #7	$214.92	3.860%	$223.2159	$223.22	$223.20	$223.20
7 purchase totals =	$951.09		$1,022.6217	$1,022.63	$1,022.55	$1,022.70