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	$195.96	8.346%	$212.3148	$212.31	$212.30	$212.30
Purchase #2	$249.79	12.370%	$280.689	$280.69	$280.70	$280.70
Purchase #3	$6.67	9.640%	$7.313	$7.31	$7.30	$7.30
Purchase #4	$248.57	8.194%	$268.9378	$268.94	$268.95	$268.90
Purchase #5	$33.61	7.422%	$36.1045	$36.10	$36.10	$36.10
Purchase #6	$124.77	3.299%	$128.8862	$128.89	$128.90	$128.90
Purchase #7	$125.50	13.390%	$142.3045	$142.30	$142.30	$142.30
7 purchase totals =	$984.87		$1,076.5498	$1,076.54	$1,076.55	$1,076.50