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	$65.91	7.565%	$70.8961	$70.90	$70.90	$70.90
Purchase #2	$46.41	8.220%	$50.2249	$50.22	$50.20	$50.20
Purchase #3	$50.45	7.542%	$54.2549	$54.25	$54.25	$54.30
Purchase #4	$135.64	5.136%	$142.6065	$142.61	$142.60	$142.60
Purchase #5	$247.83	8.512%	$268.9253	$268.93	$268.95	$268.90
Purchase #6	$197.77	8.119%	$213.8269	$213.83	$213.85	$213.80
Purchase #7	$38.30	12.782%	$43.1955	$43.20	$43.20	$43.20
7 purchase totals =	$782.31		$843.9301	$843.94	$843.95	$843.90