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	$134.25	7.403%	$144.1885	$144.19	$144.20	$144.20
Purchase #2	$77.28	6.752%	$82.4979	$82.50	$82.50	$82.50
Purchase #3	$210.26	5.166%	$221.122	$221.12	$221.10	$221.10
Purchase #4	$88.51	12.185%	$99.2949	$99.29	$99.30	$99.30
Purchase #5	$99.32	10.565%	$109.8132	$109.81	$109.80	$109.80
Purchase #6	$154.27	13.144%	$174.5472	$174.55	$174.55	$174.50
Purchase #7	$180.56	5.508%	$190.5052	$190.51	$190.50	$190.50
7 purchase totals =	$944.45		$1,021.9689	$1,021.97	$1,021.95	$1,021.90