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	$118.83	7.652%	$127.9229	$127.92	$127.90	$127.90
Purchase #2	$90.60	8.257%	$98.0808	$98.08	$98.10	$98.10
Purchase #3	$97.83	6.107%	$103.8045	$103.80	$103.80	$103.80
Purchase #4	$49.39	8.453%	$53.5649	$53.56	$53.55	$53.60
Purchase #5	$222.50	11.489%	$248.063	$248.06	$248.05	$248.10
Purchase #6	$10.27	8.689%	$11.1624	$11.16	$11.15	$11.20
Purchase #7	$45.33	13.393%	$51.401	$51.40	$51.40	$51.40
7 purchase totals =	$634.75		$693.9995	$693.98	$693.95	$694.10