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	$208.76	3.425%	$215.91	$215.91	$215.90	$215.90
Purchase #2	$218.95	11.287%	$243.6629	$243.66	$243.65	$243.70
Purchase #3	$171.82	6.112%	$182.3216	$182.32	$182.30	$182.30
Purchase #4	$192.88	3.702%	$200.0204	$200.02	$200.00	$200.00
Purchase #5	$54.40	12.861%	$61.3964	$61.40	$61.40	$61.40
Purchase #6	$205.76	8.806%	$223.8792	$223.88	$223.90	$223.90
Purchase #7	$54.33	13.618%	$61.7287	$61.73	$61.75	$61.70
7 purchase totals =	$1,106.90		$1,188.9192	$1,188.92	$1,188.90	$1,188.90