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	$134.57	13.603%	$152.8756	$152.88	$152.90	$152.90
Purchase #2	$45.31	13.594%	$51.4694	$51.47	$51.45	$51.50
Purchase #3	$96.98	7.168%	$103.9315	$103.93	$103.95	$103.90
Purchase #4	$154.59	13.716%	$175.7936	$175.79	$175.80	$175.80
Purchase #5	$46.96	9.668%	$51.5001	$51.50	$51.50	$51.50
Purchase #6	$211.80	8.721%	$230.2711	$230.27	$230.25	$230.30
Purchase #7	$181.36	11.635%	$202.4612	$202.46	$202.45	$202.50
7 purchase totals =	$871.57		$968.3025	$968.30	$968.30	$968.40