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	$128.54	13.689%	$146.1358	$146.14	$146.15	$146.10
Purchase #2	$86.72	8.749%	$94.3071	$94.31	$94.30	$94.30
Purchase #3	$166.47	12.654%	$187.5351	$187.54	$187.55	$187.50
Purchase #4	$217.33	5.623%	$229.5505	$229.55	$229.55	$229.60
Purchase #5	$133.52	6.293%	$141.9224	$141.92	$141.90	$141.90
Purchase #6	$216.98	9.771%	$238.1811	$238.18	$238.20	$238.20
Purchase #7	$200.75	5.466%	$211.723	$211.72	$211.70	$211.70
7 purchase totals =	$1,150.31		$1,249.3550	$1,249.36	$1,249.35	$1,249.30