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	$67.83	6.304%	$72.106	$72.11	$72.10	$72.10
Purchase #2	$143.35	4.263%	$149.461	$149.46	$149.45	$149.50
Purchase #3	$241.58	9.821%	$265.3056	$265.31	$265.30	$265.30
Purchase #4	$230.59	5.301%	$242.8136	$242.81	$242.80	$242.80
Purchase #5	$156.61	4.754%	$164.0552	$164.06	$164.05	$164.10
Purchase #6	$116.67	5.506%	$123.0939	$123.09	$123.10	$123.10
Purchase #7	$58.30	5.696%	$61.6208	$61.62	$61.60	$61.60
7 purchase totals =	$1,014.93		$1,078.4561	$1,078.46	$1,078.40	$1,078.50