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	$203.91	5.810%	$215.7572	$215.76	$215.75	$215.80
Purchase #2	$243.33	13.723%	$276.7222	$276.72	$276.70	$276.70
Purchase #3	$46.96	8.479%	$50.9417	$50.94	$50.95	$50.90
Purchase #4	$90.79	6.706%	$96.8784	$96.88	$96.90	$96.90
Purchase #5	$48.37	12.435%	$54.3848	$54.38	$54.40	$54.40
Purchase #6	$192.46	6.705%	$205.3644	$205.36	$205.35	$205.40
Purchase #7	$110.94	5.832%	$117.41	$117.41	$117.40	$117.40
7 purchase totals =	$936.76		$1,017.4587	$1,017.45	$1,017.45	$1,017.50