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	$105.34	11.841%	$117.8133	$117.81	$117.80	$117.80
Purchase #2	$50.45	10.565%	$55.78	$55.78	$55.80	$55.80
Purchase #3	$131.61	3.764%	$136.5638	$136.56	$136.55	$136.60
Purchase #4	$241.27	9.791%	$264.8927	$264.89	$264.90	$264.90
Purchase #5	$145.69	3.550%	$150.862	$150.86	$150.85	$150.90
Purchase #6	$231.38	13.232%	$261.9962	$262.00	$262.00	$262.00
Purchase #7	$185.54	5.615%	$195.9581	$195.96	$195.95	$196.00
7 purchase totals =	$1,091.28		$1,183.8661	$1,183.86	$1,183.85	$1,184.00