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	$171.86	7.224%	$184.2752	$184.28	$184.30	$184.30
Purchase #2	$228.85	5.670%	$241.8258	$241.83	$241.85	$241.80
Purchase #3	$158.57	3.798%	$164.5925	$164.59	$164.60	$164.60
Purchase #4	$165.49	11.568%	$184.6339	$184.63	$184.65	$184.60
Purchase #5	$174.87	12.280%	$196.344	$196.34	$196.35	$196.30
Purchase #6	$71.99	13.733%	$81.8764	$81.88	$81.90	$81.90
Purchase #7	$203.62	9.384%	$222.7277	$222.73	$222.75	$222.70
7 purchase totals =	$1,175.25		$1,276.2755	$1,276.28	$1,276.40	$1,276.20