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	$186.49	9.420%	$204.0574	$204.06	$204.05	$204.10
Purchase #2	$245.45	3.856%	$254.9146	$254.91	$254.90	$254.90
Purchase #3	$89.47	12.715%	$100.8461	$100.85	$100.85	$100.80
Purchase #4	$208.71	5.842%	$220.9028	$220.90	$220.90	$220.90
Purchase #5	$98.35	11.711%	$109.8678	$109.87	$109.85	$109.90
Purchase #6	$171.31	6.174%	$181.8867	$181.89	$181.90	$181.90
Purchase #7	$185.25	5.241%	$194.959	$194.96	$194.95	$195.00
7 purchase totals =	$1,185.03		$1,267.4344	$1,267.44	$1,267.40	$1,267.50