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	$185.26	13.653%	$210.5535	$210.55	$210.55	$210.60
Purchase #2	$23.97	4.261%	$24.9914	$24.99	$25.00	$25.00
Purchase #3	$140.92	6.860%	$150.5871	$150.59	$150.60	$150.60
Purchase #4	$55.44	7.522%	$59.6102	$59.61	$59.60	$59.60
Purchase #5	$168.51	6.777%	$179.9299	$179.93	$179.95	$179.90
Purchase #6	$196.27	10.516%	$216.9098	$216.91	$216.90	$216.90
Purchase #7	$45.72	4.595%	$47.8208	$47.82	$47.80	$47.80
7 purchase totals =	$816.09		$890.4027	$890.40	$890.40	$890.40