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	$102.33	9.675%	$112.2304	$112.23	$112.25	$112.20
Purchase #2	$63.25	3.594%	$65.5232	$65.52	$65.50	$65.50
Purchase #3	$39.25	5.122%	$41.2604	$41.26	$41.25	$41.30
Purchase #4	$9.63	12.487%	$10.8325	$10.83	$10.85	$10.80
Purchase #5	$13.53	6.361%	$14.3906	$14.39	$14.40	$14.40
Purchase #6	$119.88	9.163%	$130.8646	$130.86	$130.85	$130.90
Purchase #7	$168.76	12.482%	$189.8246	$189.82	$189.80	$189.80
7 purchase totals =	$516.63		$564.9263	$564.91	$564.90	$564.90