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	$145.98	4.322%	$152.2893	$152.29	$152.30	$152.30
Purchase #2	$202.96	9.302%	$221.8393	$221.84	$221.85	$221.80
Purchase #3	$78.82	5.238%	$82.9486	$82.95	$82.95	$82.90
Purchase #4	$6.34	6.755%	$6.7683	$6.77	$6.75	$6.80
Purchase #5	$240.89	10.158%	$265.3596	$265.36	$265.35	$265.40
Purchase #6	$224.69	3.770%	$233.1608	$233.16	$233.15	$233.20
Purchase #7	$81.28	5.615%	$85.8439	$85.84	$85.85	$85.80
7 purchase totals =	$980.96		$1,048.2098	$1,048.21	$1,048.20	$1,048.20