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	$159.73	9.293%	$174.5737	$174.57	$174.55	$174.60
Purchase #2	$203.53	12.798%	$229.5778	$229.58	$229.60	$229.60
Purchase #3	$174.88	12.290%	$196.3728	$196.37	$196.35	$196.40
Purchase #4	$56.28	11.172%	$62.5676	$62.57	$62.55	$62.60
Purchase #5	$126.31	11.820%	$141.2398	$141.24	$141.25	$141.20
Purchase #6	$56.42	13.831%	$64.2235	$64.22	$64.20	$64.20
Purchase #7	$107.72	6.372%	$114.5839	$114.58	$114.60	$114.60
7 purchase totals =	$884.87		$983.1391	$983.13	$983.10	$983.20