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	$77.56	12.632%	$87.3574	$87.36	$87.35	$87.40
Purchase #2	$151.51	7.286%	$162.549	$162.55	$162.55	$162.50
Purchase #3	$235.50	12.144%	$264.0991	$264.10	$264.10	$264.10
Purchase #4	$199.40	13.666%	$226.65	$226.65	$226.65	$226.70
Purchase #5	$96.82	6.149%	$102.7735	$102.77	$102.75	$102.80
Purchase #6	$152.40	8.280%	$165.0187	$165.02	$165.00	$165.00
Purchase #7	$70.30	12.243%	$78.9068	$78.91	$78.90	$78.90
7 purchase totals =	$983.49		$1,087.3545	$1,087.36	$1,087.30	$1,087.40