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	$70.85	3.798%	$73.5409	$73.54	$73.55	$73.50
Purchase #2	$45.35	11.501%	$50.5657	$50.57	$50.55	$50.60
Purchase #3	$39.58	6.750%	$42.2517	$42.25	$42.25	$42.30
Purchase #4	$88.72	3.374%	$91.7134	$91.71	$91.70	$91.70
Purchase #5	$132.45	13.587%	$150.446	$150.45	$150.45	$150.40
Purchase #6	$25.93	13.851%	$29.5216	$29.52	$29.50	$29.50
Purchase #7	$115.94	6.157%	$123.0784	$123.08	$123.10	$123.10
7 purchase totals =	$518.82		$561.1177	$561.12	$561.10	$561.10