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	$98.82	6.342%	$105.0872	$105.09	$105.10	$105.10
Purchase #2	$162.88	7.552%	$175.1807	$175.18	$175.20	$175.20
Purchase #3	$235.94	12.127%	$264.5524	$264.55	$264.55	$264.60
Purchase #4	$35.88	7.421%	$38.5427	$38.54	$38.55	$38.50
Purchase #5	$120.72	6.716%	$128.8276	$128.83	$128.85	$128.80
Purchase #6	$221.50	11.796%	$247.6281	$247.63	$247.65	$247.60
Purchase #7	$191.96	3.603%	$198.8763	$198.88	$198.90	$198.90
7 purchase totals =	$1,067.70		$1,158.6950	$1,158.70	$1,158.80	$1,158.70