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	$167.62	7.435%	$180.0825	$180.08	$180.10	$180.10
Purchase #2	$192.92	8.286%	$208.9054	$208.91	$208.90	$208.90
Purchase #3	$107.65	3.455%	$111.3693	$111.37	$111.35	$111.40
Purchase #4	$178.84	5.362%	$188.4294	$188.43	$188.45	$188.40
Purchase #5	$211.45	10.618%	$233.9018	$233.90	$233.90	$233.90
Purchase #6	$38.39	11.173%	$42.6793	$42.68	$42.70	$42.70
Purchase #7	$122.77	3.350%	$126.8828	$126.88	$126.90	$126.90
7 purchase totals =	$1,019.64		$1,092.2505	$1,092.25	$1,092.30	$1,092.30