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	$106.83	4.213%	$111.3307	$111.33	$111.35	$111.30
Purchase #2	$62.96	9.512%	$68.9488	$68.95	$68.95	$68.90
Purchase #3	$96.93	7.741%	$104.4334	$104.43	$104.45	$104.40
Purchase #4	$80.86	11.333%	$90.0239	$90.02	$90.00	$90.00
Purchase #5	$211.65	6.168%	$224.7046	$224.70	$224.70	$224.70
Purchase #6	$220.55	5.305%	$232.2502	$232.25	$232.25	$232.30
Purchase #7	$162.93	5.127%	$171.2834	$171.28	$171.30	$171.30
7 purchase totals =	$942.71		$1,002.9750	$1,002.96	$1,003.00	$1,002.90