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	$92.95	10.264%	$102.4904	$102.49	$102.50	$102.50
Purchase #2	$225.99	12.791%	$254.8964	$254.90	$254.90	$254.90
Purchase #3	$215.80	8.334%	$233.7848	$233.78	$233.80	$233.80
Purchase #4	$51.54	11.671%	$57.5552	$57.56	$57.55	$57.60
Purchase #5	$72.76	13.424%	$82.5273	$82.53	$82.55	$82.50
Purchase #6	$77.78	10.384%	$85.8567	$85.86	$85.85	$85.90
Purchase #7	$173.78	11.668%	$194.0567	$194.06	$194.05	$194.10
7 purchase totals =	$910.60		$1,011.1675	$1,011.18	$1,011.20	$1,011.30