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	$47.35	4.687%	$49.5693	$49.57	$49.55	$49.60
Purchase #2	$116.38	13.362%	$131.9307	$131.93	$131.95	$131.90
Purchase #3	$75.46	7.578%	$81.1784	$81.18	$81.20	$81.20
Purchase #4	$134.61	4.689%	$140.9219	$140.92	$140.90	$140.90
Purchase #5	$81.48	12.792%	$91.9029	$91.90	$91.90	$91.90
Purchase #6	$49.66	5.479%	$52.3809	$52.38	$52.40	$52.40
Purchase #7	$130.37	12.543%	$146.7223	$146.72	$146.70	$146.70
7 purchase totals =	$635.31		$694.6064	$694.60	$694.60	$694.60