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	$218.75	4.813%	$229.2784	$229.28	$229.30	$229.30
Purchase #2	$26.83	11.436%	$29.8983	$29.90	$29.90	$29.90
Purchase #3	$118.26	4.352%	$123.4067	$123.41	$123.40	$123.40
Purchase #4	$218.43	6.753%	$233.1806	$233.18	$233.20	$233.20
Purchase #5	$42.30	6.562%	$45.0757	$45.08	$45.10	$45.10
Purchase #6	$219.85	12.589%	$247.5269	$247.53	$247.55	$247.50
Purchase #7	$18.57	8.147%	$20.0829	$20.08	$20.10	$20.10
7 purchase totals =	$862.99		$928.4495	$928.46	$928.55	$928.50