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	$5.73	5.804%	$6.0626	$6.06	$6.05	$6.10
Purchase #2	$60.95	11.323%	$67.8514	$67.85	$67.85	$67.90
Purchase #3	$222.94	4.520%	$233.0169	$233.02	$233.00	$233.00
Purchase #4	$180.56	12.500%	$203.13	$203.13	$203.15	$203.10
Purchase #5	$204.34	13.215%	$231.3435	$231.34	$231.35	$231.30
Purchase #6	$96.37	5.589%	$101.7561	$101.76	$101.75	$101.80
Purchase #7	$199.38	4.540%	$208.4319	$208.43	$208.45	$208.40
7 purchase totals =	$970.27		$1,051.5924	$1,051.59	$1,051.60	$1,051.60