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	$196.80	6.592%	$209.7731	$209.77	$209.75	$209.80
Purchase #2	$200.34	5.460%	$211.2786	$211.28	$211.30	$211.30
Purchase #3	$108.45	3.224%	$111.9464	$111.95	$111.95	$111.90
Purchase #4	$98.57	4.601%	$103.1052	$103.11	$103.10	$103.10
Purchase #5	$205.69	9.574%	$225.3828	$225.38	$225.40	$225.40
Purchase #6	$116.89	12.722%	$131.7607	$131.76	$131.75	$131.80
Purchase #7	$76.99	11.850%	$86.1133	$86.11	$86.10	$86.10
7 purchase totals =	$1,003.73		$1,079.3601	$1,079.36	$1,079.35	$1,079.40