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	$55.87	11.155%	$62.1023	$62.10	$62.10	$62.10
Purchase #2	$147.93	12.829%	$166.9079	$166.91	$166.90	$166.90
Purchase #3	$99.85	5.710%	$105.5514	$105.55	$105.55	$105.60
Purchase #4	$100.89	12.107%	$113.1048	$113.10	$113.10	$113.10
Purchase #5	$81.44	10.264%	$89.799	$89.80	$89.80	$89.80
Purchase #6	$68.72	6.157%	$72.9511	$72.95	$72.95	$73.00
Purchase #7	$149.50	3.870%	$155.2857	$155.29	$155.30	$155.30
7 purchase totals =	$704.20		$765.7022	$765.70	$765.70	$765.80