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	$75.75	12.506%	$85.2233	$85.22	$85.20	$85.20
Purchase #2	$154.73	3.462%	$160.0868	$160.09	$160.10	$160.10
Purchase #3	$76.36	11.749%	$85.3315	$85.33	$85.35	$85.30
Purchase #4	$178.54	11.588%	$199.2292	$199.23	$199.25	$199.20
Purchase #5	$86.69	11.745%	$96.8717	$96.87	$96.85	$96.90
Purchase #6	$209.28	7.439%	$224.8483	$224.85	$224.85	$224.80
Purchase #7	$158.42	4.214%	$165.0958	$165.10	$165.10	$165.10
7 purchase totals =	$939.77		$1,016.6866	$1,016.69	$1,016.70	$1,016.60