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	$188.33	11.739%	$210.4381	$210.44	$210.45	$210.40
Purchase #2	$134.79	11.633%	$150.4701	$150.47	$150.45	$150.50
Purchase #3	$86.68	4.869%	$90.9004	$90.90	$90.90	$90.90
Purchase #4	$167.90	10.804%	$186.0399	$186.04	$186.05	$186.00
Purchase #5	$236.54	4.229%	$246.5433	$246.54	$246.55	$246.50
Purchase #6	$67.76	7.349%	$72.7397	$72.74	$72.75	$72.70
Purchase #7	$93.77	10.816%	$103.9122	$103.91	$103.90	$103.90
7 purchase totals =	$975.77		$1,061.0437	$1,061.04	$1,061.05	$1,060.90