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	$151.57	7.175%	$162.4451	$162.45	$162.45	$162.40
Purchase #2	$90.60	9.849%	$99.5232	$99.52	$99.50	$99.50
Purchase #3	$7.27	4.651%	$7.6081	$7.61	$7.60	$7.60
Purchase #4	$236.80	10.844%	$262.4786	$262.48	$262.50	$262.50
Purchase #5	$165.49	9.324%	$180.9203	$180.92	$180.90	$180.90
Purchase #6	$168.33	3.860%	$174.8275	$174.83	$174.85	$174.80
Purchase #7	$197.69	3.345%	$204.3027	$204.30	$204.30	$204.30
7 purchase totals =	$1,017.75		$1,092.1055	$1,092.11	$1,092.10	$1,092.00