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	$106.84	11.214%	$118.821	$118.82	$118.80	$118.80
Purchase #2	$56.36	10.504%	$62.2801	$62.28	$62.30	$62.30
Purchase #3	$170.33	4.714%	$178.3594	$178.36	$178.35	$178.40
Purchase #4	$184.56	3.260%	$190.5767	$190.58	$190.60	$190.60
Purchase #5	$97.37	13.818%	$110.8246	$110.82	$110.80	$110.80
Purchase #6	$248.88	7.739%	$268.1408	$268.14	$268.15	$268.10
Purchase #7	$111.42	10.570%	$123.1971	$123.20	$123.20	$123.20
7 purchase totals =	$975.76		$1,052.1997	$1,052.20	$1,052.20	$1,052.20