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	$28.90	11.560%	$32.2408	$32.24	$32.25	$32.20
Purchase #2	$72.87	13.781%	$82.9122	$82.91	$82.90	$82.90
Purchase #3	$235.91	12.112%	$264.4834	$264.48	$264.50	$264.50
Purchase #4	$174.94	12.256%	$196.3806	$196.38	$196.40	$196.40
Purchase #5	$62.66	11.721%	$70.0044	$70.00	$70.00	$70.00
Purchase #6	$196.66	8.655%	$213.6809	$213.68	$213.70	$213.70
Purchase #7	$43.45	8.755%	$47.254	$47.25	$47.25	$47.30
7 purchase totals =	$815.39		$906.9563	$906.94	$907.00	$907.00