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	$101.64	3.368%	$105.0632	$105.06	$105.05	$105.10
Purchase #2	$61.82	10.681%	$68.423	$68.42	$68.40	$68.40
Purchase #3	$179.88	11.270%	$200.1525	$200.15	$200.15	$200.20
Purchase #4	$226.27	5.557%	$238.8438	$238.84	$238.85	$238.80
Purchase #5	$53.42	11.371%	$59.4944	$59.49	$59.50	$59.50
Purchase #6	$117.44	11.664%	$131.1382	$131.14	$131.15	$131.10
Purchase #7	$62.62	11.102%	$69.5721	$69.57	$69.55	$69.60
7 purchase totals =	$803.09		$872.6872	$872.67	$872.65	$872.70