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	$145.58	3.294%	$150.3754	$150.38	$150.40	$150.40
Purchase #2	$131.91	6.703%	$140.7519	$140.75	$140.75	$140.80
Purchase #3	$224.31	9.445%	$245.4961	$245.50	$245.50	$245.50
Purchase #4	$221.55	7.827%	$238.8907	$238.89	$238.90	$238.90
Purchase #5	$154.88	6.474%	$164.9069	$164.91	$164.90	$164.90
Purchase #6	$50.88	6.613%	$54.2447	$54.24	$54.25	$54.20
Purchase #7	$189.98	3.253%	$196.16	$196.16	$196.15	$196.20
7 purchase totals =	$1,119.09		$1,190.8257	$1,190.83	$1,190.85	$1,190.90