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	$228.58	11.482%	$254.8256	$254.83	$254.85	$254.80
Purchase #2	$171.57	3.397%	$177.3982	$177.40	$177.40	$177.40
Purchase #3	$184.47	6.460%	$196.3868	$196.39	$196.40	$196.40
Purchase #4	$188.75	3.779%	$195.8829	$195.88	$195.90	$195.90
Purchase #5	$245.64	7.812%	$264.8294	$264.83	$264.85	$264.80
Purchase #6	$12.27	3.796%	$12.7358	$12.74	$12.75	$12.70
Purchase #7	$38.96	7.407%	$41.8458	$41.85	$41.85	$41.80
7 purchase totals =	$1,070.24		$1,143.9045	$1,143.92	$1,144.00	$1,143.80