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	$149.36	3.405%	$154.4457	$154.45	$154.45	$154.40
Purchase #2	$100.59	4.705%	$105.3228	$105.32	$105.30	$105.30
Purchase #3	$52.47	7.699%	$56.5097	$56.51	$56.50	$56.50
Purchase #4	$155.72	10.310%	$171.7747	$171.77	$171.75	$171.80
Purchase #5	$80.97	10.829%	$89.7382	$89.74	$89.75	$89.70
Purchase #6	$162.55	6.566%	$173.223	$173.22	$173.20	$173.20
Purchase #7	$142.98	9.829%	$157.0335	$157.03	$157.05	$157.00
7 purchase totals =	$844.64		$908.0476	$908.04	$908.00	$907.90