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	$80.63	7.611%	$86.7667	$86.77	$86.75	$86.80
Purchase #2	$17.65	9.550%	$19.3356	$19.34	$19.35	$19.30
Purchase #3	$136.37	11.233%	$151.6884	$151.69	$151.70	$151.70
Purchase #4	$67.50	7.355%	$72.4646	$72.46	$72.45	$72.50
Purchase #5	$115.29	10.872%	$127.8243	$127.82	$127.80	$127.80
Purchase #6	$55.92	7.435%	$60.0777	$60.08	$60.10	$60.10
Purchase #7	$114.74	8.819%	$124.8589	$124.86	$124.85	$124.90
7 purchase totals =	$588.10		$643.0162	$643.02	$643.00	$643.10