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	$150.85	7.268%	$161.8138	$161.81	$161.80	$161.80
Purchase #2	$89.33	7.846%	$96.3388	$96.34	$96.35	$96.30
Purchase #3	$100.58	12.654%	$113.3074	$113.31	$113.30	$113.30
Purchase #4	$230.46	3.448%	$238.4063	$238.41	$238.40	$238.40
Purchase #5	$65.37	3.206%	$67.4658	$67.47	$67.45	$67.50
Purchase #6	$41.96	4.770%	$43.9615	$43.96	$43.95	$44.00
Purchase #7	$156.77	3.818%	$162.7555	$162.76	$162.75	$162.80
7 purchase totals =	$835.32		$884.0491	$884.06	$884.00	$884.10