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	$156.61	11.450%	$174.5418	$174.54	$174.55	$174.50
Purchase #2	$65.44	4.803%	$68.5831	$68.58	$68.60	$68.60
Purchase #3	$237.27	12.533%	$267.007	$267.01	$267.00	$267.00
Purchase #4	$81.54	11.528%	$90.9399	$90.94	$90.95	$90.90
Purchase #5	$181.51	8.254%	$196.4918	$196.49	$196.50	$196.50
Purchase #6	$204.86	3.848%	$212.743	$212.74	$212.75	$212.70
Purchase #7	$92.79	6.662%	$98.9717	$98.97	$98.95	$99.00
7 purchase totals =	$1,020.02		$1,109.2783	$1,109.27	$1,109.30	$1,109.20