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	$223.90	7.259%	$240.1529	$240.15	$240.15	$240.20
Purchase #2	$168.56	6.617%	$179.7136	$179.71	$179.70	$179.70
Purchase #3	$95.64	7.306%	$102.6275	$102.63	$102.65	$102.60
Purchase #4	$35.87	11.173%	$39.8778	$39.88	$39.90	$39.90
Purchase #5	$115.83	10.790%	$128.3281	$128.33	$128.35	$128.30
Purchase #6	$207.86	8.366%	$225.2496	$225.25	$225.25	$225.20
Purchase #7	$141.87	7.743%	$152.855	$152.86	$152.85	$152.90
7 purchase totals =	$989.53		$1,068.8045	$1,068.81	$1,068.85	$1,068.80