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	$93.46	3.299%	$96.5432	$96.54	$96.55	$96.50
Purchase #2	$155.63	11.738%	$173.8978	$173.90	$173.90	$173.90
Purchase #3	$73.53	11.846%	$82.2404	$82.24	$82.25	$82.20
Purchase #4	$103.48	8.569%	$112.3472	$112.35	$112.35	$112.30
Purchase #5	$121.70	9.551%	$133.3236	$133.32	$133.30	$133.30
Purchase #6	$179.65	6.355%	$191.0668	$191.07	$191.05	$191.10
Purchase #7	$219.86	4.744%	$230.2902	$230.29	$230.30	$230.30
7 purchase totals =	$947.31		$1,019.7092	$1,019.71	$1,019.70	$1,019.60