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	$149.76	12.241%	$168.0921	$168.09	$168.10	$168.10
Purchase #2	$188.80	6.113%	$200.3413	$200.34	$200.35	$200.30
Purchase #3	$168.87	8.209%	$182.7325	$182.73	$182.75	$182.70
Purchase #4	$225.83	8.734%	$245.554	$245.55	$245.55	$245.60
Purchase #5	$82.30	8.298%	$89.1293	$89.13	$89.15	$89.10
Purchase #6	$77.28	11.770%	$86.3759	$86.38	$86.40	$86.40
Purchase #7	$94.84	5.218%	$99.7888	$99.79	$99.80	$99.80
7 purchase totals =	$987.68		$1,072.0139	$1,072.01	$1,072.10	$1,072.00