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	$159.44	4.301%	$166.2975	$166.30	$166.30	$166.30
Purchase #2	$196.82	3.836%	$204.37	$204.37	$204.35	$204.40
Purchase #3	$209.28	6.294%	$222.4521	$222.45	$222.45	$222.50
Purchase #4	$124.88	13.108%	$141.2493	$141.25	$141.25	$141.20
Purchase #5	$99.25	6.661%	$105.861	$105.86	$105.85	$105.90
Purchase #6	$176.31	5.560%	$186.1128	$186.11	$186.10	$186.10
Purchase #7	$218.59	7.793%	$235.6247	$235.62	$235.60	$235.60
7 purchase totals =	$1,184.57		$1,261.9674	$1,261.96	$1,261.90	$1,262.00