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	$70.25	10.641%	$77.7253	$77.73	$77.75	$77.70
Purchase #2	$103.97	5.721%	$109.9181	$109.92	$109.90	$109.90
Purchase #3	$101.88	10.484%	$112.5611	$112.56	$112.55	$112.60
Purchase #4	$120.43	9.510%	$131.8829	$131.88	$131.90	$131.90
Purchase #5	$189.71	4.796%	$198.8085	$198.81	$198.80	$198.80
Purchase #6	$235.64	9.559%	$258.1648	$258.16	$258.15	$258.20
Purchase #7	$109.47	10.415%	$120.8713	$120.87	$120.85	$120.90
7 purchase totals =	$931.35		$1,009.9320	$1,009.93	$1,009.90	$1,010.00