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	$85.25	4.487%	$89.0752	$89.08	$89.10	$89.10
Purchase #2	$228.88	9.165%	$249.8569	$249.86	$249.85	$249.90
Purchase #3	$196.71	7.315%	$211.0993	$211.10	$211.10	$211.10
Purchase #4	$223.77	12.856%	$252.5379	$252.54	$252.55	$252.50
Purchase #5	$81.87	9.107%	$89.3259	$89.33	$89.35	$89.30
Purchase #6	$109.51	7.708%	$117.951	$117.95	$117.95	$118.00
Purchase #7	$106.35	10.393%	$117.403	$117.40	$117.40	$117.40
7 purchase totals =	$1,032.34		$1,127.2492	$1,127.26	$1,127.30	$1,127.30