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	$64.90	3.827%	$67.3837	$67.38	$67.40	$67.40
Purchase #2	$238.78	3.209%	$246.4425	$246.44	$246.45	$246.40
Purchase #3	$164.87	4.167%	$171.7401	$171.74	$171.75	$171.70
Purchase #4	$62.29	4.872%	$65.3248	$65.32	$65.30	$65.30
Purchase #5	$186.46	5.687%	$197.064	$197.06	$197.05	$197.10
Purchase #6	$171.63	8.323%	$185.9148	$185.91	$185.90	$185.90
Purchase #7	$164.72	12.767%	$185.7498	$185.75	$185.75	$185.70
7 purchase totals =	$1,053.65		$1,119.6197	$1,119.60	$1,119.60	$1,119.50