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	$184.91	4.175%	$192.63	$192.63	$192.65	$192.60
Purchase #2	$51.77	11.164%	$57.5496	$57.55	$57.55	$57.50
Purchase #3	$114.33	11.678%	$127.6815	$127.68	$127.70	$127.70
Purchase #4	$190.80	11.305%	$212.3699	$212.37	$212.35	$212.40
Purchase #5	$157.53	4.459%	$164.5543	$164.55	$164.55	$164.60
Purchase #6	$222.34	12.445%	$250.0102	$250.01	$250.00	$250.00
Purchase #7	$160.61	9.159%	$175.3203	$175.32	$175.30	$175.30
7 purchase totals =	$1,082.29		$1,180.1158	$1,180.11	$1,180.10	$1,180.10