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	$99.34	9.804%	$109.0793	$109.08	$109.10	$109.10
Purchase #2	$70.99	8.741%	$77.1952	$77.20	$77.20	$77.20
Purchase #3	$128.33	5.378%	$135.2316	$135.23	$135.25	$135.20
Purchase #4	$72.47	8.726%	$78.7937	$78.79	$78.80	$78.80
Purchase #5	$92.73	7.260%	$99.4622	$99.46	$99.45	$99.50
Purchase #6	$38.48	12.766%	$43.3924	$43.39	$43.40	$43.40
Purchase #7	$167.46	7.152%	$179.4367	$179.44	$179.45	$179.40
7 purchase totals =	$669.80		$722.5911	$722.59	$722.65	$722.60