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	$56.52	4.794%	$59.2296	$59.23	$59.25	$59.20
Purchase #2	$56.89	5.372%	$59.9461	$59.95	$59.95	$59.90
Purchase #3	$102.68	12.398%	$115.4103	$115.41	$115.40	$115.40
Purchase #4	$188.77	6.373%	$200.8003	$200.80	$200.80	$200.80
Purchase #5	$42.96	10.568%	$47.5	$47.50	$47.50	$47.50
Purchase #6	$168.34	8.479%	$182.6135	$182.61	$182.60	$182.60
Purchase #7	$124.87	5.520%	$131.7628	$131.76	$131.75	$131.80
7 purchase totals =	$741.03		$797.2626	$797.26	$797.25	$797.20