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	$54.47	8.178%	$58.9246	$58.92	$58.90	$58.90
Purchase #2	$170.33	5.284%	$179.3302	$179.33	$179.35	$179.30
Purchase #3	$51.39	7.659%	$55.326	$55.33	$55.35	$55.30
Purchase #4	$62.41	4.775%	$65.3901	$65.39	$65.40	$65.40
Purchase #5	$94.76	5.157%	$99.6468	$99.65	$99.65	$99.60
Purchase #6	$237.99	8.566%	$258.3762	$258.38	$258.40	$258.40
Purchase #7	$196.42	7.570%	$211.289	$211.29	$211.30	$211.30
7 purchase totals =	$867.77		$928.2829	$928.29	$928.35	$928.20