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	$62.92	8.284%	$68.1323	$68.13	$68.15	$68.10
Purchase #2	$43.55	9.812%	$47.8231	$47.82	$47.80	$47.80
Purchase #3	$133.31	13.279%	$151.0122	$151.01	$151.00	$151.00
Purchase #4	$249.78	3.543%	$258.6297	$258.63	$258.65	$258.60
Purchase #5	$183.57	3.467%	$189.9344	$189.93	$189.95	$189.90
Purchase #6	$215.96	6.301%	$229.5676	$229.57	$229.55	$229.60
Purchase #7	$96.72	3.334%	$99.9446	$99.94	$99.95	$99.90
7 purchase totals =	$985.81		$1,045.0439	$1,045.03	$1,045.05	$1,044.90