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	$50.46	10.859%	$55.9395	$55.94	$55.95	$55.90
Purchase #2	$235.54	10.294%	$259.7865	$259.79	$259.80	$259.80
Purchase #3	$148.40	13.535%	$168.4859	$168.49	$168.50	$168.50
Purchase #4	$159.89	3.236%	$165.064	$165.06	$165.05	$165.10
Purchase #5	$137.91	5.363%	$145.3061	$145.31	$145.30	$145.30
Purchase #6	$161.62	10.847%	$179.1509	$179.15	$179.15	$179.20
Purchase #7	$239.82	6.229%	$254.7584	$254.76	$254.75	$254.80
7 purchase totals =	$1,133.64		$1,228.4913	$1,228.50	$1,228.50	$1,228.60