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	$39.37	13.704%	$44.7653	$44.77	$44.75	$44.80
Purchase #2	$118.93	3.641%	$123.2602	$123.26	$123.25	$123.30
Purchase #3	$77.44	6.260%	$82.2877	$82.29	$82.30	$82.30
Purchase #4	$223.30	12.533%	$251.2862	$251.29	$251.30	$251.30
Purchase #5	$201.84	10.862%	$223.7639	$223.76	$223.75	$223.80
Purchase #6	$104.98	5.153%	$110.3896	$110.39	$110.40	$110.40
Purchase #7	$247.91	10.407%	$273.71	$273.71	$273.70	$273.70
7 purchase totals =	$1,013.77		$1,109.4629	$1,109.47	$1,109.45	$1,109.60