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	$111.57	10.740%	$123.5526	$123.55	$123.55	$123.60
Purchase #2	$17.30	3.865%	$17.9686	$17.97	$17.95	$18.00
Purchase #3	$6.37	3.847%	$6.6151	$6.62	$6.60	$6.60
Purchase #4	$121.43	12.336%	$136.4096	$136.41	$136.40	$136.40
Purchase #5	$92.88	9.695%	$101.8847	$101.88	$101.90	$101.90
Purchase #6	$216.31	3.360%	$223.578	$223.58	$223.60	$223.60
Purchase #7	$168.80	9.795%	$185.334	$185.33	$185.35	$185.30
7 purchase totals =	$734.66		$795.3426	$795.34	$795.35	$795.40