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	$89.90	13.220%	$101.7848	$101.78	$101.80	$101.80
Purchase #2	$100.47	8.516%	$109.026	$109.03	$109.05	$109.00
Purchase #3	$154.54	9.824%	$169.722	$169.72	$169.70	$169.70
Purchase #4	$102.97	9.498%	$112.7501	$112.75	$112.75	$112.80
Purchase #5	$215.26	4.628%	$225.2222	$225.22	$225.20	$225.20
Purchase #6	$165.70	12.171%	$185.8673	$185.87	$185.85	$185.90
Purchase #7	$117.49	9.739%	$128.9324	$128.93	$128.95	$128.90
7 purchase totals =	$946.33		$1,033.3048	$1,033.30	$1,033.30	$1,033.30