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	$26.69	6.632%	$28.4601	$28.46	$28.45	$28.50
Purchase #2	$20.32	10.476%	$22.4487	$22.45	$22.45	$22.40
Purchase #3	$162.38	6.377%	$172.735	$172.74	$172.75	$172.70
Purchase #4	$120.85	5.495%	$127.4907	$127.49	$127.50	$127.50
Purchase #5	$29.64	4.737%	$31.044	$31.04	$31.05	$31.00
Purchase #6	$67.73	6.295%	$71.9936	$71.99	$72.00	$72.00
Purchase #7	$230.30	6.497%	$245.2626	$245.26	$245.25	$245.30
7 purchase totals =	$657.91		$699.4347	$699.43	$699.45	$699.40