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	$103.64	5.218%	$109.0479	$109.05	$109.05	$109.00
Purchase #2	$153.64	6.860%	$164.1797	$164.18	$164.20	$164.20
Purchase #3	$200.55	7.649%	$215.8901	$215.89	$215.90	$215.90
Purchase #4	$153.38	13.820%	$174.5771	$174.58	$174.60	$174.60
Purchase #5	$186.84	6.193%	$198.411	$198.41	$198.40	$198.40
Purchase #6	$48.95	8.584%	$53.1519	$53.15	$53.15	$53.20
Purchase #7	$79.39	12.152%	$89.0375	$89.04	$89.05	$89.00
7 purchase totals =	$926.39		$1,004.2952	$1,004.30	$1,004.35	$1,004.30