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	$119.46	7.621%	$128.564	$128.56	$128.55	$128.60
Purchase #2	$136.31	10.807%	$151.041	$151.04	$151.05	$151.00
Purchase #3	$114.50	5.365%	$120.6429	$120.64	$120.65	$120.60
Purchase #4	$136.47	13.820%	$155.3302	$155.33	$155.35	$155.30
Purchase #5	$21.94	4.420%	$22.9097	$22.91	$22.90	$22.90
Purchase #6	$140.46	10.435%	$155.117	$155.12	$155.10	$155.10
Purchase #7	$152.30	7.677%	$163.9921	$163.99	$164.00	$164.00
7 purchase totals =	$821.44		$897.5969	$897.59	$897.60	$897.50