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	$118.95	10.167%	$131.0436	$131.04	$131.05	$131.00
Purchase #2	$30.52	4.571%	$31.9151	$31.92	$31.90	$31.90
Purchase #3	$51.97	6.349%	$55.2696	$55.27	$55.25	$55.30
Purchase #4	$61.60	9.391%	$67.3849	$67.38	$67.40	$67.40
Purchase #5	$207.27	9.627%	$227.2239	$227.22	$227.20	$227.20
Purchase #6	$111.52	6.488%	$118.7554	$118.76	$118.75	$118.80
Purchase #7	$130.55	12.618%	$147.0228	$147.02	$147.00	$147.00
7 purchase totals =	$712.38		$778.6153	$778.61	$778.55	$778.60