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	$165.57	9.530%	$181.3488	$181.35	$181.35	$181.30
Purchase #2	$51.54	5.829%	$54.5443	$54.54	$54.55	$54.50
Purchase #3	$28.58	11.326%	$31.817	$31.82	$31.80	$31.80
Purchase #4	$76.76	5.778%	$81.1952	$81.20	$81.20	$81.20
Purchase #5	$59.91	12.774%	$67.5629	$67.56	$67.55	$67.60
Purchase #6	$133.96	8.148%	$144.8751	$144.88	$144.90	$144.90
Purchase #7	$81.60	6.540%	$86.9366	$86.94	$86.95	$86.90
7 purchase totals =	$597.92		$648.2799	$648.29	$648.30	$648.20