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	$150.73	3.587%	$156.1367	$156.14	$156.15	$156.10
Purchase #2	$210.53	12.108%	$236.021	$236.02	$236.00	$236.00
Purchase #3	$106.85	12.571%	$120.2821	$120.28	$120.30	$120.30
Purchase #4	$199.91	7.808%	$215.519	$215.52	$215.50	$215.50
Purchase #5	$74.61	10.478%	$82.4276	$82.43	$82.45	$82.40
Purchase #6	$59.29	6.812%	$63.3288	$63.33	$63.35	$63.30
Purchase #7	$129.37	10.280%	$142.6692	$142.67	$142.65	$142.70
7 purchase totals =	$931.29		$1,016.3844	$1,016.39	$1,016.40	$1,016.30