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	$165.26	10.199%	$182.1149	$182.11	$182.10	$182.10
Purchase #2	$33.82	6.620%	$36.0589	$36.06	$36.05	$36.10
Purchase #3	$191.75	4.769%	$200.8946	$200.89	$200.90	$200.90
Purchase #4	$198.54	11.234%	$220.844	$220.84	$220.85	$220.80
Purchase #5	$157.57	4.400%	$164.5031	$164.50	$164.50	$164.50
Purchase #6	$181.60	5.585%	$191.7424	$191.74	$191.75	$191.70
Purchase #7	$168.95	10.364%	$186.46	$186.46	$186.45	$186.50
7 purchase totals =	$1,097.49		$1,182.6179	$1,182.60	$1,182.60	$1,182.60