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	$145.32	8.227%	$157.2755	$157.28	$157.30	$157.30
Purchase #2	$143.28	9.130%	$156.3615	$156.36	$156.35	$156.40
Purchase #3	$215.86	3.371%	$223.1366	$223.14	$223.15	$223.10
Purchase #4	$227.81	13.371%	$258.2705	$258.27	$258.25	$258.30
Purchase #5	$40.36	7.184%	$43.2595	$43.26	$43.25	$43.30
Purchase #6	$196.31	4.218%	$204.5904	$204.59	$204.60	$204.60
Purchase #7	$54.76	5.347%	$57.688	$57.69	$57.70	$57.70
7 purchase totals =	$1,023.70		$1,100.5820	$1,100.59	$1,100.60	$1,100.70