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	$133.96	5.370%	$141.1537	$141.15	$141.15	$141.20
Purchase #2	$35.98	13.173%	$40.7196	$40.72	$40.70	$40.70
Purchase #3	$67.61	6.242%	$71.8302	$71.83	$71.85	$71.80
Purchase #4	$182.86	6.434%	$194.6252	$194.63	$194.65	$194.60
Purchase #5	$54.84	5.372%	$57.786	$57.79	$57.80	$57.80
Purchase #6	$140.98	11.792%	$157.6044	$157.60	$157.60	$157.60
Purchase #7	$39.25	8.543%	$42.6031	$42.60	$42.60	$42.60
7 purchase totals =	$655.48		$706.3222	$706.32	$706.35	$706.30