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	$98.55	3.601%	$102.0988	$102.10	$102.10	$102.10
Purchase #2	$150.93	7.499%	$162.2482	$162.25	$162.25	$162.20
Purchase #3	$165.62	5.366%	$174.5072	$174.51	$174.50	$174.50
Purchase #4	$56.98	10.308%	$62.8535	$62.85	$62.85	$62.90
Purchase #5	$144.75	7.657%	$155.8335	$155.83	$155.85	$155.80
Purchase #6	$104.66	6.651%	$111.6209	$111.62	$111.60	$111.60
Purchase #7	$244.49	10.543%	$270.2666	$270.27	$270.25	$270.30
7 purchase totals =	$965.98		$1,039.4287	$1,039.43	$1,039.40	$1,039.40