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	$226.86	8.685%	$246.5628	$246.56	$246.55	$246.60
Purchase #2	$202.99	11.594%	$226.5247	$226.52	$226.50	$226.50
Purchase #3	$188.33	7.698%	$202.8276	$202.83	$202.85	$202.80
Purchase #4	$225.93	8.627%	$245.421	$245.42	$245.40	$245.40
Purchase #5	$77.45	11.391%	$86.2723	$86.27	$86.25	$86.30
Purchase #6	$28.59	9.209%	$31.2229	$31.22	$31.20	$31.20
Purchase #7	$98.37	13.592%	$111.7405	$111.74	$111.75	$111.70
7 purchase totals =	$1,048.52		$1,150.5718	$1,150.56	$1,150.50	$1,150.50