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	$194.96	12.484%	$219.2988	$219.30	$219.30	$219.30
Purchase #2	$189.37	12.303%	$212.6682	$212.67	$212.65	$212.70
Purchase #3	$179.37	6.553%	$191.1241	$191.12	$191.10	$191.10
Purchase #4	$100.73	9.360%	$110.1583	$110.16	$110.15	$110.20
Purchase #5	$166.38	12.436%	$187.071	$187.07	$187.05	$187.10
Purchase #6	$44.40	8.712%	$48.2681	$48.27	$48.25	$48.30
Purchase #7	$102.82	8.323%	$111.3777	$111.38	$111.40	$111.40
7 purchase totals =	$978.03		$1,079.9662	$1,079.97	$1,079.90	$1,080.10