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	$138.59	4.503%	$144.8307	$144.83	$144.85	$144.80
Purchase #2	$73.48	7.383%	$78.905	$78.91	$78.90	$78.90
Purchase #3	$138.58	6.496%	$147.5822	$147.58	$147.60	$147.60
Purchase #4	$119.84	6.628%	$127.783	$127.78	$127.80	$127.80
Purchase #5	$84.81	13.262%	$96.0575	$96.06	$96.05	$96.10
Purchase #6	$215.99	3.310%	$223.1393	$223.14	$223.15	$223.10
Purchase #7	$119.65	7.255%	$128.3306	$128.33	$128.35	$128.30
7 purchase totals =	$890.94		$946.6283	$946.63	$946.70	$946.60