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	$67.85	8.516%	$73.6281	$73.63	$73.65	$73.60
Purchase #2	$27.58	13.223%	$31.2269	$31.23	$31.25	$31.20
Purchase #3	$178.63	4.376%	$186.4468	$186.45	$186.45	$186.40
Purchase #4	$141.82	6.246%	$150.6781	$150.68	$150.70	$150.70
Purchase #5	$75.85	3.549%	$78.5419	$78.54	$78.55	$78.50
Purchase #6	$174.67	4.632%	$182.7607	$182.76	$182.75	$182.80
Purchase #7	$79.64	12.612%	$89.6842	$89.68	$89.70	$89.70
7 purchase totals =	$746.04		$792.9667	$792.97	$793.05	$792.90