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	$177.36	5.459%	$187.0421	$187.04	$187.05	$187.00
Purchase #2	$111.94	6.599%	$119.3269	$119.33	$119.35	$119.30
Purchase #3	$50.35	8.692%	$54.7264	$54.73	$54.75	$54.70
Purchase #4	$194.85	7.794%	$210.0366	$210.04	$210.05	$210.00
Purchase #5	$116.98	5.588%	$123.5168	$123.52	$123.50	$123.50
Purchase #6	$80.54	12.751%	$90.8097	$90.81	$90.80	$90.80
Purchase #7	$116.84	6.176%	$124.056	$124.06	$124.05	$124.10
7 purchase totals =	$848.86		$909.5145	$909.53	$909.55	$909.40