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	$71.82	7.764%	$77.3961	$77.40	$77.40	$77.40
Purchase #2	$104.55	13.172%	$118.3213	$118.32	$118.30	$118.30
Purchase #3	$51.82	11.388%	$57.7213	$57.72	$57.70	$57.70
Purchase #4	$70.25	12.166%	$78.7966	$78.80	$78.80	$78.80
Purchase #5	$80.40	7.454%	$86.393	$86.39	$86.40	$86.40
Purchase #6	$167.29	8.178%	$180.971	$180.97	$180.95	$181.00
Purchase #7	$246.88	8.873%	$268.7857	$268.79	$268.80	$268.80
7 purchase totals =	$793.01		$868.3850	$868.39	$868.35	$868.40