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	$133.85	6.397%	$142.4124	$142.41	$142.40	$142.40
Purchase #2	$240.45	4.283%	$250.7485	$250.75	$250.75	$250.70
Purchase #3	$100.37	3.708%	$104.0917	$104.09	$104.10	$104.10
Purchase #4	$240.55	10.395%	$265.5552	$265.56	$265.55	$265.60
Purchase #5	$39.77	9.355%	$43.4905	$43.49	$43.50	$43.50
Purchase #6	$158.83	7.865%	$171.322	$171.32	$171.30	$171.30
Purchase #7	$89.96	7.497%	$96.7043	$96.70	$96.70	$96.70
7 purchase totals =	$1,003.78		$1,074.3246	$1,074.32	$1,074.30	$1,074.30