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	$156.46	8.247%	$169.3633	$169.36	$169.35	$169.40
Purchase #2	$100.90	10.633%	$111.6287	$111.63	$111.65	$111.60
Purchase #3	$206.49	7.360%	$221.6877	$221.69	$221.70	$221.70
Purchase #4	$152.30	10.801%	$168.7499	$168.75	$168.75	$168.70
Purchase #5	$184.76	3.447%	$191.1287	$191.13	$191.15	$191.10
Purchase #6	$47.72	10.201%	$52.5879	$52.59	$52.60	$52.60
Purchase #7	$123.48	10.577%	$136.5405	$136.54	$136.55	$136.50
7 purchase totals =	$972.11		$1,051.6867	$1,051.69	$1,051.75	$1,051.60