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	$165.98	7.791%	$178.9115	$178.91	$178.90	$178.90
Purchase #2	$11.29	12.838%	$12.7394	$12.74	$12.75	$12.70
Purchase #3	$142.97	13.704%	$162.5626	$162.56	$162.55	$162.60
Purchase #4	$233.36	3.313%	$241.0912	$241.09	$241.10	$241.10
Purchase #5	$147.56	12.812%	$166.4654	$166.47	$166.45	$166.50
Purchase #6	$47.46	12.173%	$53.2373	$53.24	$53.25	$53.20
Purchase #7	$184.59	8.505%	$200.2894	$200.29	$200.30	$200.30
7 purchase totals =	$933.21		$1,015.2968	$1,015.30	$1,015.30	$1,015.30