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	$85.94	12.214%	$96.4367	$96.44	$96.45	$96.40
Purchase #2	$86.74	3.270%	$89.5764	$89.58	$89.60	$89.60
Purchase #3	$174.83	4.840%	$183.2918	$183.29	$183.30	$183.30
Purchase #4	$101.78	13.807%	$115.8328	$115.83	$115.85	$115.80
Purchase #5	$62.70	5.766%	$66.3153	$66.32	$66.30	$66.30
Purchase #6	$11.73	5.804%	$12.4108	$12.41	$12.40	$12.40
Purchase #7	$62.70	13.791%	$71.347	$71.35	$71.35	$71.30
7 purchase totals =	$586.42		$635.2108	$635.22	$635.25	$635.10