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	$80.85	5.788%	$85.5296	$85.53	$85.55	$85.50
Purchase #2	$85.54	12.766%	$96.46	$96.46	$96.45	$96.50
Purchase #3	$196.41	3.463%	$203.2117	$203.21	$203.20	$203.20
Purchase #4	$148.96	11.627%	$166.2796	$166.28	$166.30	$166.30
Purchase #5	$186.56	13.791%	$212.2885	$212.29	$212.30	$212.30
Purchase #6	$108.93	8.645%	$118.347	$118.35	$118.35	$118.30
Purchase #7	$179.32	11.453%	$199.8575	$199.86	$199.85	$199.90
7 purchase totals =	$986.57		$1,081.9739	$1,081.98	$1,082.00	$1,082.00