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	$52.70	5.806%	$55.7598	$55.76	$55.75	$55.80
Purchase #2	$5.64	7.804%	$6.0801	$6.08	$6.10	$6.10
Purchase #3	$96.49	5.323%	$101.6262	$101.63	$101.65	$101.60
Purchase #4	$211.60	3.410%	$218.8156	$218.82	$218.80	$218.80
Purchase #5	$203.47	12.222%	$228.3381	$228.34	$228.35	$228.30
Purchase #6	$38.92	11.194%	$43.2767	$43.28	$43.30	$43.30
Purchase #7	$86.40	3.657%	$89.5596	$89.56	$89.55	$89.60
7 purchase totals =	$695.22		$743.4561	$743.47	$743.50	$743.50