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	$76.59	8.706%	$83.2579	$83.26	$83.25	$83.30
Purchase #2	$155.46	12.463%	$174.835	$174.84	$174.85	$174.80
Purchase #3	$114.87	10.313%	$126.7165	$126.72	$126.70	$126.70
Purchase #4	$64.41	12.629%	$72.5443	$72.54	$72.55	$72.50
Purchase #5	$109.88	7.675%	$118.3133	$118.31	$118.30	$118.30
Purchase #6	$152.57	6.359%	$162.2719	$162.27	$162.25	$162.30
Purchase #7	$177.67	7.145%	$190.3645	$190.36	$190.35	$190.40
7 purchase totals =	$851.45		$928.3034	$928.30	$928.25	$928.30