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	$30.32	3.559%	$31.3991	$31.40	$31.40	$31.40
Purchase #2	$81.41	10.546%	$89.9955	$90.00	$90.00	$90.00
Purchase #3	$53.94	13.298%	$61.1129	$61.11	$61.10	$61.10
Purchase #4	$249.83	4.811%	$261.8493	$261.85	$261.85	$261.80
Purchase #5	$90.33	7.300%	$96.9241	$96.92	$96.90	$96.90
Purchase #6	$223.73	6.502%	$238.2769	$238.28	$238.30	$238.30
Purchase #7	$231.37	6.348%	$246.0574	$246.06	$246.05	$246.10
7 purchase totals =	$960.93		$1,025.6152	$1,025.62	$1,025.60	$1,025.60