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	$94.50	11.710%	$105.566	$105.57	$105.55	$105.60
Purchase #2	$107.81	7.583%	$115.9852	$115.99	$116.00	$116.00
Purchase #3	$118.59	8.592%	$128.7793	$128.78	$128.80	$128.80
Purchase #4	$246.43	5.701%	$260.479	$260.48	$260.50	$260.50
Purchase #5	$221.73	7.350%	$238.0272	$238.03	$238.05	$238.00
Purchase #6	$159.26	12.623%	$179.3634	$179.36	$179.35	$179.40
Purchase #7	$88.54	12.290%	$99.4216	$99.42	$99.40	$99.40
7 purchase totals =	$1,036.86		$1,127.6217	$1,127.63	$1,127.65	$1,127.70