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	$58.91	6.201%	$62.563	$62.56	$62.55	$62.60
Purchase #2	$245.37	11.124%	$272.665	$272.67	$272.65	$272.70
Purchase #3	$171.41	5.336%	$180.5564	$180.56	$180.55	$180.60
Purchase #4	$74.44	5.640%	$78.6384	$78.64	$78.65	$78.60
Purchase #5	$171.92	5.217%	$180.8891	$180.89	$180.90	$180.90
Purchase #6	$65.25	11.649%	$72.851	$72.85	$72.85	$72.90
Purchase #7	$234.85	7.210%	$251.7827	$251.78	$251.80	$251.80
7 purchase totals =	$1,022.15		$1,099.9456	$1,099.95	$1,099.95	$1,100.10