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	$78.25	5.288%	$82.3879	$82.39	$82.40	$82.40
Purchase #2	$102.69	11.542%	$114.5425	$114.54	$114.55	$114.50
Purchase #3	$66.80	5.738%	$70.633	$70.63	$70.65	$70.60
Purchase #4	$179.28	10.844%	$198.7211	$198.72	$198.70	$198.70
Purchase #5	$185.72	6.796%	$198.3415	$198.34	$198.35	$198.30
Purchase #6	$37.36	11.829%	$41.7793	$41.78	$41.80	$41.80
Purchase #7	$141.57	4.494%	$147.9322	$147.93	$147.95	$147.90
7 purchase totals =	$791.67		$854.3375	$854.33	$854.40	$854.20