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	$110.41	4.247%	$115.0991	$115.10	$115.10	$115.10
Purchase #2	$122.77	4.323%	$128.0773	$128.08	$128.10	$128.10
Purchase #3	$153.38	13.510%	$174.1016	$174.10	$174.10	$174.10
Purchase #4	$188.97	13.721%	$214.8986	$214.90	$214.90	$214.90
Purchase #5	$126.28	3.166%	$130.278	$130.28	$130.30	$130.30
Purchase #6	$136.95	9.732%	$150.278	$150.28	$150.30	$150.30
Purchase #7	$99.51	7.218%	$106.6926	$106.69	$106.70	$106.70
7 purchase totals =	$938.27		$1,019.4252	$1,019.43	$1,019.50	$1,019.50