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	$147.53	3.552%	$152.7703	$152.77	$152.75	$152.80
Purchase #2	$209.64	9.477%	$229.5076	$229.51	$229.50	$229.50
Purchase #3	$194.32	11.482%	$216.6318	$216.63	$216.65	$216.60
Purchase #4	$232.73	11.320%	$259.075	$259.08	$259.10	$259.10
Purchase #5	$70.51	8.661%	$76.6169	$76.62	$76.60	$76.60
Purchase #6	$58.77	11.102%	$65.2946	$65.29	$65.30	$65.30
Purchase #7	$149.95	12.665%	$168.9412	$168.94	$168.95	$168.90
7 purchase totals =	$1,063.45		$1,168.8374	$1,168.84	$1,168.85	$1,168.80