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	$79.81	7.700%	$85.9554	$85.96	$85.95	$86.00
Purchase #2	$245.39	6.285%	$260.8128	$260.81	$260.80	$260.80
Purchase #3	$185.47	6.843%	$198.1617	$198.16	$198.15	$198.20
Purchase #4	$76.54	4.379%	$79.8917	$79.89	$79.90	$79.90
Purchase #5	$131.76	8.849%	$143.4194	$143.42	$143.40	$143.40
Purchase #6	$233.97	4.264%	$243.9465	$243.95	$243.95	$243.90
Purchase #7	$79.37	9.445%	$86.8665	$86.87	$86.85	$86.90
7 purchase totals =	$1,032.31		$1,099.0540	$1,099.06	$1,099.00	$1,099.10