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	$176.32	12.319%	$198.0409	$198.04	$198.05	$198.00
Purchase #2	$59.31	11.874%	$66.3525	$66.35	$66.35	$66.40
Purchase #3	$11.77	4.793%	$12.3341	$12.33	$12.35	$12.30
Purchase #4	$31.34	9.735%	$34.3909	$34.39	$34.40	$34.40
Purchase #5	$148.73	11.813%	$166.2995	$166.30	$166.30	$166.30
Purchase #6	$89.55	11.740%	$100.0632	$100.06	$100.05	$100.10
Purchase #7	$100.28	5.259%	$105.5537	$105.55	$105.55	$105.60
7 purchase totals =	$617.30		$683.0348	$683.02	$683.05	$683.10