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	$99.96	11.824%	$111.7793	$111.78	$111.80	$111.80
Purchase #2	$231.39	11.438%	$257.8564	$257.86	$257.85	$257.90
Purchase #3	$59.98	13.444%	$68.0437	$68.04	$68.05	$68.00
Purchase #4	$9.74	12.216%	$10.9298	$10.93	$10.95	$10.90
Purchase #5	$184.58	7.582%	$198.5749	$198.57	$198.55	$198.60
Purchase #6	$40.46	6.221%	$42.977	$42.98	$43.00	$43.00
Purchase #7	$38.35	12.633%	$43.1948	$43.19	$43.20	$43.20
7 purchase totals =	$664.46		$733.3559	$733.35	$733.40	$733.40