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	$168.86	11.716%	$188.6436	$188.64	$188.65	$188.60
Purchase #2	$81.92	11.658%	$91.4702	$91.47	$91.45	$91.50
Purchase #3	$36.30	12.485%	$40.8321	$40.83	$40.85	$40.80
Purchase #4	$177.88	10.317%	$196.2319	$196.23	$196.25	$196.20
Purchase #5	$110.71	6.394%	$117.7888	$117.79	$117.80	$117.80
Purchase #6	$249.27	3.453%	$257.8773	$257.88	$257.90	$257.90
Purchase #7	$221.92	3.441%	$229.5563	$229.56	$229.55	$229.60
7 purchase totals =	$1,046.86		$1,122.4002	$1,122.40	$1,122.45	$1,122.40