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	$123.51	3.215%	$127.4808	$127.48	$127.50	$127.50
Purchase #2	$235.89	8.693%	$256.3959	$256.40	$256.40	$256.40
Purchase #3	$108.51	6.644%	$115.7194	$115.72	$115.70	$115.70
Purchase #4	$96.25	3.362%	$99.4859	$99.49	$99.50	$99.50
Purchase #5	$188.34	5.257%	$198.241	$198.24	$198.25	$198.20
Purchase #6	$106.51	7.525%	$114.5249	$114.52	$114.50	$114.50
Purchase #7	$94.87	4.636%	$99.2682	$99.27	$99.25	$99.30
7 purchase totals =	$953.88		$1,011.1161	$1,011.12	$1,011.10	$1,011.10