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	$216.88	5.376%	$228.5395	$228.54	$228.55	$228.50
Purchase #2	$52.30	13.223%	$59.2156	$59.22	$59.20	$59.20
Purchase #3	$181.39	9.819%	$199.2007	$199.20	$199.20	$199.20
Purchase #4	$156.37	10.826%	$173.2986	$173.30	$173.30	$173.30
Purchase #5	$189.71	7.131%	$203.2382	$203.24	$203.25	$203.20
Purchase #6	$150.42	6.479%	$160.1657	$160.17	$160.15	$160.20
Purchase #7	$40.48	3.435%	$41.8705	$41.87	$41.85	$41.90
7 purchase totals =	$987.55		$1,065.5288	$1,065.54	$1,065.50	$1,065.50