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	$50.53	7.163%	$54.1495	$54.15	$54.15	$54.10
Purchase #2	$183.53	3.423%	$189.8122	$189.81	$189.80	$189.80
Purchase #3	$45.64	7.414%	$49.0237	$49.02	$49.00	$49.00
Purchase #4	$190.35	3.162%	$196.3689	$196.37	$196.35	$196.40
Purchase #5	$70.37	7.563%	$75.6921	$75.69	$75.70	$75.70
Purchase #6	$164.78	5.827%	$174.3817	$174.38	$174.40	$174.40
Purchase #7	$99.78	9.338%	$109.0975	$109.10	$109.10	$109.10
7 purchase totals =	$804.98		$848.5256	$848.52	$848.50	$848.50