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	$129.30	12.418%	$145.3565	$145.36	$145.35	$145.40
Purchase #2	$96.84	6.469%	$103.1046	$103.10	$103.10	$103.10
Purchase #3	$179.45	11.300%	$199.7279	$199.73	$199.75	$199.70
Purchase #4	$209.49	11.234%	$233.0241	$233.02	$233.00	$233.00
Purchase #5	$71.37	3.313%	$73.7345	$73.73	$73.75	$73.70
Purchase #6	$138.42	4.389%	$144.4953	$144.50	$144.50	$144.50
Purchase #7	$141.73	9.123%	$154.66	$154.66	$154.65	$154.70
7 purchase totals =	$966.60		$1,054.1029	$1,054.10	$1,054.10	$1,054.10