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	$166.59	7.229%	$178.6328	$178.63	$178.65	$178.60
Purchase #2	$166.58	3.336%	$172.1371	$172.14	$172.15	$172.10
Purchase #3	$62.99	6.635%	$67.1694	$67.17	$67.15	$67.20
Purchase #4	$172.33	7.360%	$185.0135	$185.01	$185.00	$185.00
Purchase #5	$191.81	9.214%	$209.4834	$209.48	$209.50	$209.50
Purchase #6	$114.28	8.661%	$124.1778	$124.18	$124.20	$124.20
Purchase #7	$10.72	10.794%	$11.8771	$11.88	$11.90	$11.90
7 purchase totals =	$885.30		$948.4911	$948.49	$948.55	$948.50