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	$72.53	8.106%	$78.4093	$78.41	$78.40	$78.40
Purchase #2	$22.88	6.507%	$24.3688	$24.37	$24.35	$24.40
Purchase #3	$29.42	13.164%	$33.2928	$33.29	$33.30	$33.30
Purchase #4	$121.44	9.421%	$132.8809	$132.88	$132.90	$132.90
Purchase #5	$62.39	12.364%	$70.1039	$70.10	$70.10	$70.10
Purchase #6	$199.42	11.811%	$222.9735	$222.97	$222.95	$223.00
Purchase #7	$243.91	8.365%	$264.3131	$264.31	$264.30	$264.30
7 purchase totals =	$751.99		$826.3423	$826.33	$826.30	$826.40