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	$165.79	11.729%	$185.2355	$185.24	$185.25	$185.20
Purchase #2	$131.63	8.161%	$142.3723	$142.37	$142.35	$142.40
Purchase #3	$30.56	9.796%	$33.5537	$33.55	$33.55	$33.60
Purchase #4	$162.89	5.567%	$171.9581	$171.96	$171.95	$172.00
Purchase #5	$129.53	11.628%	$144.5917	$144.59	$144.60	$144.60
Purchase #6	$109.91	9.798%	$120.679	$120.68	$120.70	$120.70
Purchase #7	$205.81	5.315%	$216.7488	$216.75	$216.75	$216.70
7 purchase totals =	$936.12		$1,015.1391	$1,015.14	$1,015.15	$1,015.20