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	$242.56	6.404%	$258.0935	$258.09	$258.10	$258.10
Purchase #2	$38.44	11.623%	$42.9079	$42.91	$42.90	$42.90
Purchase #3	$186.94	12.351%	$210.029	$210.03	$210.05	$210.00
Purchase #4	$141.80	3.344%	$146.5418	$146.54	$146.55	$146.50
Purchase #5	$196.75	9.557%	$215.5534	$215.55	$215.55	$215.60
Purchase #6	$150.28	9.435%	$164.4589	$164.46	$164.45	$164.50
Purchase #7	$43.56	6.470%	$46.3783	$46.38	$46.40	$46.40
7 purchase totals =	$1,000.33		$1,083.9628	$1,083.96	$1,084.00	$1,084.00