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	$150.26	4.427%	$156.912	$156.91	$156.90	$156.90
Purchase #2	$93.81	12.217%	$105.2708	$105.27	$105.25	$105.30
Purchase #3	$164.40	13.498%	$186.5907	$186.59	$186.60	$186.60
Purchase #4	$115.80	6.825%	$123.7034	$123.70	$123.70	$123.70
Purchase #5	$229.63	9.577%	$251.6217	$251.62	$251.60	$251.60
Purchase #6	$248.99	4.144%	$259.3081	$259.31	$259.30	$259.30
Purchase #7	$59.54	10.765%	$65.9495	$65.95	$65.95	$65.90
7 purchase totals =	$1,062.43		$1,149.3562	$1,149.35	$1,149.30	$1,149.30