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	$90.46	6.578%	$96.4105	$96.41	$96.40	$96.40
Purchase #2	$86.41	4.790%	$90.549	$90.55	$90.55	$90.50
Purchase #3	$147.35	11.131%	$163.7515	$163.75	$163.75	$163.80
Purchase #4	$191.26	4.820%	$200.4787	$200.48	$200.50	$200.50
Purchase #5	$158.89	7.661%	$171.0626	$171.06	$171.05	$171.10
Purchase #6	$59.56	9.274%	$65.0836	$65.08	$65.10	$65.10
Purchase #7	$114.27	5.874%	$120.9822	$120.98	$121.00	$121.00
7 purchase totals =	$848.20		$908.3181	$908.31	$908.35	$908.40