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	$50.47	13.463%	$57.2648	$57.26	$57.25	$57.30
Purchase #2	$117.72	6.397%	$125.2505	$125.25	$125.25	$125.30
Purchase #3	$58.69	12.277%	$65.8954	$65.90	$65.90	$65.90
Purchase #4	$82.70	3.556%	$85.6408	$85.64	$85.65	$85.60
Purchase #5	$179.62	11.389%	$200.0769	$200.08	$200.10	$200.10
Purchase #6	$124.73	11.464%	$139.029	$139.03	$139.05	$139.00
Purchase #7	$29.85	11.753%	$33.3583	$33.36	$33.35	$33.40
7 purchase totals =	$643.78		$706.5157	$706.52	$706.55	$706.60