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	$209.31	9.421%	$229.0291	$229.03	$229.05	$229.00
Purchase #2	$112.91	13.403%	$128.0433	$128.04	$128.05	$128.00
Purchase #3	$107.25	3.383%	$110.8783	$110.88	$110.90	$110.90
Purchase #4	$125.32	8.568%	$136.0574	$136.06	$136.05	$136.10
Purchase #5	$184.39	6.536%	$196.4417	$196.44	$196.45	$196.40
Purchase #6	$46.75	13.333%	$52.9832	$52.98	$53.00	$53.00
Purchase #7	$154.85	6.822%	$165.4139	$165.41	$165.40	$165.40
7 purchase totals =	$940.78		$1,018.8469	$1,018.84	$1,018.90	$1,018.80