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	$245.46	3.185%	$253.2779	$253.28	$253.30	$253.30
Purchase #2	$237.76	9.832%	$261.1366	$261.14	$261.15	$261.10
Purchase #3	$76.47	7.837%	$82.463	$82.46	$82.45	$82.50
Purchase #4	$232.64	7.156%	$249.2877	$249.29	$249.30	$249.30
Purchase #5	$81.75	13.617%	$92.8819	$92.88	$92.90	$92.90
Purchase #6	$13.98	3.690%	$14.4959	$14.50	$14.50	$14.50
Purchase #7	$91.67	11.170%	$101.9095	$101.91	$101.90	$101.90
7 purchase totals =	$979.73		$1,055.4525	$1,055.46	$1,055.50	$1,055.50