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	$202.76	4.265%	$211.4077	$211.41	$211.40	$211.40
Purchase #2	$14.88	9.236%	$16.2543	$16.25	$16.25	$16.30
Purchase #3	$18.56	12.832%	$20.9416	$20.94	$20.95	$20.90
Purchase #4	$87.90	13.531%	$99.7937	$99.79	$99.80	$99.80
Purchase #5	$131.27	3.864%	$136.3423	$136.34	$136.35	$136.30
Purchase #6	$73.59	3.788%	$76.3776	$76.38	$76.40	$76.40
Purchase #7	$37.69	12.323%	$42.3345	$42.33	$42.35	$42.30
7 purchase totals =	$566.65		$603.4517	$603.44	$603.50	$603.40