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	$160.66	9.508%	$175.9356	$175.94	$175.95	$175.90
Purchase #2	$43.93	7.319%	$47.1452	$47.15	$47.15	$47.10
Purchase #3	$73.69	6.685%	$78.6162	$78.62	$78.60	$78.60
Purchase #4	$200.41	4.303%	$209.0336	$209.03	$209.05	$209.00
Purchase #5	$144.39	5.661%	$152.5639	$152.56	$152.55	$152.60
Purchase #6	$215.88	6.681%	$230.3029	$230.30	$230.30	$230.30
Purchase #7	$207.91	10.339%	$229.4058	$229.41	$229.40	$229.40
7 purchase totals =	$1,046.87		$1,123.0032	$1,123.01	$1,123.00	$1,122.90