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	$182.81	8.766%	$198.8351	$198.84	$198.85	$198.80
Purchase #2	$95.69	4.410%	$99.9099	$99.91	$99.90	$99.90
Purchase #3	$129.85	9.740%	$142.4974	$142.50	$142.50	$142.50
Purchase #4	$73.50	12.243%	$82.4986	$82.50	$82.50	$82.50
Purchase #5	$153.29	10.314%	$169.1003	$169.10	$169.10	$169.10
Purchase #6	$162.82	11.615%	$181.7315	$181.73	$181.75	$181.70
Purchase #7	$143.33	9.312%	$156.6769	$156.68	$156.70	$156.70
7 purchase totals =	$941.29		$1,031.2497	$1,031.26	$1,031.30	$1,031.20