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	$18.32	4.557%	$19.1548	$19.15	$19.15	$19.20
Purchase #2	$144.27	10.125%	$158.8773	$158.88	$158.90	$158.90
Purchase #3	$36.55	3.186%	$37.7145	$37.71	$37.70	$37.70
Purchase #4	$214.91	9.746%	$235.8551	$235.86	$235.85	$235.90
Purchase #5	$41.83	8.242%	$45.2776	$45.28	$45.30	$45.30
Purchase #6	$235.72	13.568%	$267.7025	$267.70	$267.70	$267.70
Purchase #7	$223.66	7.511%	$240.4591	$240.46	$240.45	$240.50
7 purchase totals =	$915.26		$1,005.0409	$1,005.04	$1,005.05	$1,005.20