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	$69.34	4.266%	$72.298	$72.30	$72.30	$72.30
Purchase #2	$151.33	13.543%	$171.8246	$171.82	$171.80	$171.80
Purchase #3	$29.68	7.460%	$31.8941	$31.89	$31.90	$31.90
Purchase #4	$92.52	12.279%	$103.8805	$103.88	$103.90	$103.90
Purchase #5	$247.73	9.134%	$270.3577	$270.36	$270.35	$270.40
Purchase #6	$83.79	4.299%	$87.3921	$87.39	$87.40	$87.40
Purchase #7	$169.30	3.454%	$175.1476	$175.15	$175.15	$175.10
7 purchase totals =	$843.69		$912.7946	$912.79	$912.80	$912.80