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	$81.88	10.127%	$90.172	$90.17	$90.15	$90.20
Purchase #2	$102.62	12.442%	$115.388	$115.39	$115.40	$115.40
Purchase #3	$148.31	12.126%	$166.2941	$166.29	$166.30	$166.30
Purchase #4	$98.85	4.765%	$103.5602	$103.56	$103.55	$103.60
Purchase #5	$213.97	11.245%	$238.0309	$238.03	$238.05	$238.00
Purchase #6	$141.92	3.589%	$147.0135	$147.01	$147.00	$147.00
Purchase #7	$147.32	10.462%	$162.7326	$162.73	$162.75	$162.70
7 purchase totals =	$934.87		$1,023.1913	$1,023.18	$1,023.20	$1,023.20